Wrapped rotor sleeve for an electric machine

ABSTRACT

A rotor for an electric machine may include a rotor hub, a plurality of permanent magnets disposed about the rotor hub, a first sleeve circumjacent the plurality of permanent magnets, and a second sleeve. The second sleeve may be formed from a metal tape wrapped over the first sleeve. The second sleeve may be bonded to first and second end rings disposed at adjacent ends of the rotor hub. The metal tape may be applied in tension and may wrapped to form butt laps over the first sleeve. The metal tape may be corrosion resistant. Further, the second sleeve formed from the metal tape may protect the rotor from erosion and abrasion from fluid passing over the rotor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provision Application No.61/084,238, filed Jul. 28, 2008 and U.S. Provisional Application No.61/096,290, filed Sep. 11, 2008, the entire disclosures of which areincorporated by reference herein.

BACKGROUND

Some electric machines operate to convert mechanical movement (e.g.,kinetic energy) into electrical power, convert electrical power intomechanical movement, or both. For example, an electric machine systemthat operates to convert mechanical movement into electrical power(i.e., generate electrical power) can include an electric machinecoupled to a companion device that is a prime mover. The prime moversupplies mechanical movement to the electric machine, which converts themechanical movement into electrical power. An electric machine systemconfigured to convert electrical power into mechanical movement (i.e.,motor) can include an electric machine coupled to a companion devicethat is driven by the mechanical movement output from the electricmachine. In certain instances, electric machine systems configured toboth generate electrical power and mechanical movement can include anelectric machine coupled to a companion device (e.g., a prime mover)that may be driven by the electric machine and that may drive theelectric machine.

SUMMARY

One aspect of the present disclosure encompasses a stator for anelectric machine including a rotor hub, a plurality of permanent magnetsdisposed about the rotor hub, a first sleeve circumjacent the pluralityof permanent magnets, and a second sleeve. The second sleeve may includea metal tape wrapped over the first sleeve.

According to another aspect, a method of forming a rotor for an electricmachine may include forming a first sleeve surrounding a plurality ofpermanent magnets disposed about a rotor hub and wrapping a metal tapearound the first sleeve to form a second sleeve.

According to a further aspect, an electric machine may include a stator.The stator may include a rotor hub, a plurality of permanent magnetsdisposed about the rotor hub, a first sleeve circumjacent the pluralityof permanent magnets, and a second sleeve comprising a metal tapewrapped over the first sleeve.

One or more of the aspects may include some, none, or all of thefollowing features. The wrapped metal tape may form butt laps over anouter surface of the first sleeve. The first sleeve may be anon-metallic sleeve. The first sleeve is formed from a compositematerial. First and second end rings may be disposed adjacent toopposing ends of the rotor hub. A first end of the metal tape may bebonded to the first end ring, and a second end of the metal tape may bebonded to the second end ring. The metal tape may be applied undertension. The second sleeve may be cylindrical. The metal tape may becoated with a nonconductive coating. The second sleeve may extendaxially beyond opposing edges of the first sleeve. The metal tape may benon-magnetic. A first end ring may be applied to a first end of therotor hub, and a second end ring may be applied to a second end of therotor hub. Wrapping a metal tape around the first sleeve to form asecond sleeve may include bonding a first end of the metal tape to thefirst end ring, placing the metal tape under tension while wrapping themetal tape around the first sleeve, and bonding a second end of themetal tape to the second end ring. Wrapping a metal tape around thefirst sleeve to form a second sleeve may include wrapping the metal tapein butt laps over the first sleeve. A nonconductive coating may beformed over the metal tape. The metal tape may be trimmed flush withouter surfaces of the first end plate and the second end plate.

One or more of the aspects may include some, none, or all of thefollowing features. The wrapped metal tape forms butt laps over an outersurface of the first sleeve. The first sleeve may be a non-metallicsleeve. The first sleeve may be formed from a composite material. Firstand second end rings may be disposed adjacent to opposing ends of therotor hub. A first end of the metal tape may bonded to the first endring, and a second end of the metal tape may be bonded to the second endring. The metal tape may be applied under tension. The second sleeve maybe cylindrical. The metal tape may be coated with a nonconductivecoating. The second sleeve may extend axially beyond opposing edges ofthe first sleeve. The metal tape may be non-magnetic.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features,objects, and advantages will be apparent from the description anddrawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic of an example electric machine system.

FIG. 1B is a cross-sectional view of an example electric machine systemincluding a subsea pump.

FIG. 1C is a cross-sectional view of an example electric machine systemincluding a subsea compressor.

FIG. 2A is a cross-sectional view of an example rotor.

FIG. 2B is a detail cross-sectional view of an end of the example rotorof FIG. 2A.

FIG. 2C shows an example rotor with a composite sleeve formed by ametallic tape wrapped around an outer jacket of the rotor.

FIG. 2D is a detail cross-sectional view of an end of an example rotorhaving a rotor sleeve formed from a metal alloy tape.

FIG. 2E is a detail cut-away view of an example rotor sleeve.

FIG. 2F is a detail cross-sectional view of another example rotor.

FIG. 2G is a detail, perspective view of the example rotor of FIG. 2E.

FIGS. 2H-2P are schematic cross-sectional views of different examplerotors having segmented magnets, wherein the arrows associated with eachmagnet segment represent the respective magnet segment's north poleorientation.

FIG. 2Q is a side view of an example rotor showing a plurality of flowpath channels formed by segments of the rotor magnets.

FIG. 2R is a side view of another example rotor having grooves formed inthe rotor to facilitate introduction of a filler material thereinto.

FIG. 2S is a side view of another example rotor having an annularchannel 264 formed therein along with an inlet formed in a end ringthereof.

FIG. 2T is a cross-sectional view of a magnet segment or magnet segmentrow having uniform radial magnetization.

FIG. 2U is a cross-sectional view of a magnet segment or magnet segmentrow having true radial magnetization.

FIG. 3A shows a cross-sectional view of an example electric machine.

FIG. 3B shows a perspective view of an example stator core for use in anelectric machine.

FIG. 3C shows two adjacent yoke portions formed, each yoke portionformed from a plurality of individual portions.

FIG. 3D shows an example portion used to form part of the yoke portionsof FIG. 3C.

FIG. 3E shows an example stator bar of the example stator of FIG. 3Bused to provide alignment and rigidity to the stator.

FIG. 3F is an example end plate of the example stator of FIG. 3B.

FIG. 3G is a partial detail view of an end of the example stator of FIG.3B.

FIG. 3H shows an example stator tooth lamination for use in the examplestator of FIG. 3B.

FIG. 3I shows a side view of two adjacent stator tooth laminationshaving respective protrusions and receptacles for aligning and/orattaching the stator tooth laminations.

FIG. 3J shows an alternate configuration for aligning and/or attachingadjacent stator tooth laminations.

FIG. 3K is a schematic view of tooth segments disposed in a channelformed in adjacent yokes.

FIG. 3L is a cross-sectional view of an example electric machine havinga protective barrier around the stator.

FIGS. 3M-3Q are partial cross-sectional views illustrating exampleconstructions of the protective barrier.

FIG. 4A is a partial schematic end view of an example core of a statorfor an electric machine.

FIG. 4B is a partial schematic end view of an example core of a statorfor an electric machine.

FIG. 4C is a partial schematic end view of an example core of a statorfor an electric machine.

FIG. 4D is a partial schematic end view of an example core of a statorfor an electric machine.

FIG. 4E is a partial schematic end view of an example core of a statorfor an electric machine.

FIG. 4F is a schematic end view of example end turns of a stator for anelectric machine.

FIG. 4G is a schematic end view of example end turns of a stator for anelectric machine.

FIG. 4H is a schematic side view of example end turns of a stator for anelectric machine.

FIG. 4I is a schematic side view of example end turns of a stator for anelectric machine.

FIG. 4J is a schematic cross-sectional view of an example stator for anelectric machine.

FIG. 4K is a schematic cross-sectional view of example end turns of astator for an electric machine.

FIG. 4L is a schematic of two example end turns.

FIG. 4M is a schematic of example end turns.

FIG. 4N is a schematic of example end turns.

FIG. 4O is a schematic of example end turns.

FIG. 4P is a schematic side view of example end turns of a stator for anelectric machine.

FIG. 4Q is a schematic perspective view of example end turns of a statorfor an electric machine.

FIG. 4R is a partial schematic cross-sectional view of an example coreof a stator for an electric machine.

FIG. 4S is a partial schematic cross-sectional view of an example coreof a stator for an electric machine.

FIG. 4T is a partial schematic cross-sectional view of an example coreof a stator for an electric machine.

FIG. 4U is a partial schematic cross-sectional view of an example coreof a stator for an electric machine.

FIG. 4V is a perspective view of an example wedge for insertion into oneor more stator core slots.

FIG. 4W is a wiring diagram showing connections for one phase of a threephase electric machine.

FIG. 4X is a wiring diagram showing connections for one phase of a threephase electric machine.

FIG. 4Y is a wiring diagram showing connections for one phase of a threephase electric machine.

FIG. 4Z is a partial schematic end view of an example core of a statorfor an electric machine.

FIG. 4AA is a partial schematic end view of an example core of a statorfor an electric machine.

FIG. 4BB is a partial schematic end view of an example core of a statorfor an electric machine.

FIG. 4CC is a partial schematic end view of an example core of a statorfor an electric machine.

FIG. 4DD is a partial schematic end view of an example core of a statorfor an electric machine.

FIG. 4EE is a schematic end view of example end turns of a stator for anelectric machine.

FIG. 4FF is a schematic end view of example end turns of a stator for anelectric machine.

FIG. 4GG is a schematic end view of example end turns of a stator for anelectric machine.

FIG. 4HH is a schematic side view of example end turns of a stator foran electric machine.

FIG. 4II is a schematic cross-sectional view of an example stator for anelectric machine.

FIG. 4JJ is a schematic cross-sectional view of an example stator corefor an electric machine.

FIG. 4KK is a schematic cross-sectional view of an example stator corefor an electric machine.

FIG. 4LL is a perspective view of an example wedge for insertion intoone or more stator core slots.

FIG. 4MM is a perspective view of an example wedge for insertion intoone or more stator core slots.

FIG. 4NN is a schematic end view of an example stator core for anelectric machine.

FIG. 4OO is a perspective view of an example wedge for insertion intoone or more stator core slots.

FIG. 4PP is a schematic end view of an example stator core for anelectric machine.

FIG. 4QQ is an example slot liner for a stator slot of an electricmachine.

FIG. 4RR is an end view of an example stator core for an electricmachine showing the slot liner of FIG. 4QQ residing in the slot andretained by a liner clamp.

FIG. 4SS is an end view of an example stator core for an electricmachine showing the slot liner of FIG. 4QQ residing in the slot andretained by an alternate liner clamp.

FIG. 4TT is a partial perspective view of an example stator for anelectric machine.

FIG. 4UU is an end view of an example stator for an electric machine.

FIG. 4VV is a partial perspective view of an example stator for anelectric machine.

FIG. 4WW is a partial side view of an example stator for an electricmachine.

FIG. 4XX is a partial perspective view of an example stator for anelectric machine.

DETAILED DESCRIPTION

Referring to FIG. 1A, an electric machine system 100 includes anelectric machine 102 coupled to a companion device 104. The electricmachine 102 can operate as a generator, producing electrical power frommechanical movement, operate as a motor producing mechanical movementfrom electricity, or alternate between generating electrical power andmotoring. In generating electrical power, a prime mover suppliesmechanical movement to the electric machine 102, and the electricmachine 102 converts the mechanical movement into electrical power. Incertain instances, the companion device 104 may be the prime mover. Inmotoring, the mechanical movement output from the electric machine 102can drive another device. In certain instances, the electric machine 102can drive the companion device 104. In certain instances, the electricmachine 102 can operate to motor and drive the prime mover duringspecified conditions, and switch to generating electrical power and bedriven by the prime mover during specified conditions. The electricmachine 102 can be configured for primarily generating electrical power,primarily motoring, or to be reasonably efficient at both generatingelectrical power and motoring.

In general terms, the electric machine 102 includes a stationary memberand a movable member that, by interaction of magnetic fields, generateselectrical power as the movable member moves relative to the stationarymember and/or moves the movable member as electrical power is applied tothe stationary member. For convenience of reference herein, the electricmachine 102 is described as a rotating electric machine, where themovable member is a rotor 106 supported to rotate in the stationarymember, a stator 108. Rotor 106 is coupled to the companion device 104to drive the companion device 104 and/or be driven by the companiondevice 104. While FIG. 1A illustrates a horizontally-oriented electricmachine coupled to a horizontally-oriented companion device 104, otherimplementations may provide for a vertically-oriented electric machinecoupled to and capable of driving vertically-oriented companion devices,among other orientations. Additionally, in other instances, the electricmachine 102 can be another type of electric machine. For example, theelectric machine 102 can be a linear electric machine, where the movablemember is a linearly reciprocating shaft. The linearly reciprocatingshaft may be coupled to the companion device 104 to drive and/or bedriven by the companion device 104. As described in more detail below,the electric machine 102 is an alternating current (AC), synchronous,permanent magnet (PM) electric machine having a rotor 106 that includespermanent magnets and stator 108 that includes a plurality of formed orcable windings about a core. In other instances, the electric machinecan be an other type of electric machine, such as an AC, asynchronous,induction machine where both the rotor and the stator include windingsor another type of electric machine. In certain instances, the electricmachine 102 is carried by and contained within a housing 110. Thehousing 110 can be wholly separate from the companion device 104,separate from and coupled to the companion device 104, or partially orwholly shared with the companion device 104 (i.e., the electric machine102 and companion device 104 carried by and contained within a commonhousing).

In certain instances, the electric machine system 100 may be a subseaelectric machine configured for subsea operation, submerged in the opensea (i.e., outside of a well or a pipeline). To this end, the housing110 is a pressure vessel sealed against passage of fluid between theinterior of the housing 110 and the surrounding environment (e.g., thesurrounding seawater). The housing 110 is constructed to withstand theambient pressures about the electric machine system 100 and thermalloads exerted by the surrounding environment, as well as pressures andthermal loads incurred in operating the electric machine 102 andcompanion device 104. The housing 110 may be constructed of a materialthat resists corrosion, for example, stainless steel, nickel alloys suchas Inconel a registered trademark of Special Metals Corporation, and/orother materials. The housing 110 may additionally or alternatively beplated or coated with a material that resists corrosion, for example,Inconel, epoxy, polyetheretherketone, ethylene chlorotrifluoroethyleneand/or other materials. In certain instances, the housing 110 may carryanodes (not shown) to assist in resisting corrosion. In certaininstances, the housing 110 may be coupled to a skid or other structurethat aligns with and engages (e.g., by way of guide tubes that receiveguide cones) other subsea structures.

In instances where the companion device 104 is a prime mover, thecompanion device can include a number of different possible devices. Forexample, the prime mover may include one or more of a fluid motoroperable to convert fluid (gas/liquid) flow into mechanical energy, agas turbine system operable to combust an air/fuel mixture and convertthe energy from combustion into mechanical energy, an internalcombustion engine, and/or other type of prime mover. In instances wherethe companion device 104 is driven by the electric machine 102, thecompanion device can include a number of different possible devices. Forexample, the companion device 104 can include one or more of a rotatingand/or reciprocating pump, rotating and/or reciprocating compressor,mixing device, or other device. Some examples of pumps includecentrifugal pump, axial pump, rotary vane pump, gear pump, screw pump,lobe pump, progressive cavity pump, reciprocating positive displacementor plunger pump, diaphragm pump, and/or other types of pumps. Someexamples of compressors include centrifugal compressor, axialcompressor, rotary vane compressor, screw compressor, reciprocatingpositive displacement compressor and/or other types of compressors. Theelectric machine 102 can be coupled to two or more companion devices 104at the same time.

Although shown with a single companion device 104, the electric machine102 can also be coupled to two or more companion devices 104 (to driveand/or be driven by the devices 104). In certain instances, one or morecompanion devices 104 can be provided at each end of the electricmachine 102. For example, in a configuration with two companion devices104, one may be provided at one end of the electric machine 102 andanother provided at an opposing end of the electric machine. In anotherexample, a configuration with two companion devices 104 can have oneprovided at one end of the electric machine 102, and another coupled tothe first companion device. Also, if multiple companion devices 104 areprovided, they need not all be of the same type of companion device.

FIG. 1B depicts an example electric machine system 100 a where thecompanion device 104 a is a pump driven by the electric machine 102 a.One pump companion device 104 a is shown. In other instances, more pumpcompanion devices 104 a can be provided. For example, two pump companiondevices 104 a could be provided on opposing ends of the electric machine102 a (e.g., in a configuration similar to the compressor companiondevices 104 b shown below). In certain instances, two or more pumpcompanion devices 104 a could be provided on the same side of theelectric machine 102 a. The example electric machine system 100 a isconfigured for subsea operation, submerged in the open sea (i.e.,outside of a well). In other words, the example electric machine system100 a is a subsea pump system.

The housing 110 a is a pressure vessel sealed against passage of fluidbetween the interior of the housing 110 a and the surroundingenvironment (e.g., the surrounding seawater). In certain instances, thehousing is flooded with a heat transfer fluid that is communicated toboth the rotor 106 and the stator 108. In certain instances, the heattransfer fluid includes a liquid, is primarily a liquid and/or isentirely liquid. The heat transfer fluid can include water,mono-ethylene glycol (MEG), mono-propylene glycol (MPG), an oil, a fluidsimilar to or the same as that being pumped by the pump companion device104 a, and/or other fluid. Although referred to herein as a heattransfer fluid, the fluid may perform functions other than to provideheat transfer with the electric machine 102 a. In certain instances, thefluid lubricates bearing surfaces and/or performs other functions. Incertain instances, the heat transfer fluid is maintained at pressureabove the maximum operating pressure attained by the pump companiondevice 104 a. Because the heat transfer fluid is at a pressure above themaximum operating pressure attained by the pump companion device 104 a,leakage between the electric machine 102 a and the pump companion device104 tends to be leakage of the heat transfer fluid towards the pumpcompanion device 104 a. In certain instances, the pressure of the heattransfer fluid is above the ambient pressure about the exterior of theelectric machine system 100 a by an amount substantially greater thanthe incidental pressure incurred in circulating the heat transfer fluidsthrough the electric machine system 100 a. The housing 110 a has aflange 112 proximate the drive end of the electric machine 102 a. Flange112 is configured to be sealingly joined, by bolts and/or otherwise, tothe companion device 104 a, for example, at a corresponding flange 124of the companion device 104 a. In certain instances, a seal (e.g., ringgasket, o-ring and/or other) may be provided between flange 112 andflange 124. FIG. 1B depicts a close-coupled subsea pump system, in thatthe housing 110 a of the electric machine 102 a attaches directly to thehousing 148 of the pump companion device 104 a. In other instances, thesubsea pump system can be of an integrated configuration where theelectric machine and companion device have a common housing and/orcommon shaft. For example, in some common housing configurations, thehousing body that surrounds both the electric machine and the companiondevice can be a unitary piece (i.e., not readily separable, such as byremoval of fasteners). In some common shaft configurations, the rotor ofthe electric machine can be unitary with the drive shaft of thecompanion device (i.e., not readily separable, such as by removal offasteners or by release of the drive coupling). In other instances,subsea pump system can be of a non-integrated configuration having thehousing of electric machine 102 a wholly separate (not coupled and/orsubstantially coupled) from the housing of the pump companion device 104a.

The housing 110 a as shown is configured in four main elements includinga housing body 114, a drive end plate 116 a proximate the drive end ofthe electric machine 102 a, a non-drive end plate 118 a opposite thedrive end of the electric machine 102 a, and an end cap 119 at the endof the housing body 114 adjacent the non-drive end plate 118 a. Incertain instances, the housing 110 a may be configured in fewer or moreelements. One or more seals 120 (e.g. gaskets, o-rings and/or other) maybe provided between the end cap 119 and the housing body 114 to sealagainst passage of fluid into and/or out of the housing 110 a. Incertain instances, seals may additionally or alternatively be providedbetween the drive end plate 116 a and the housing body 114 and/orbetween the non-drive end plate 118 a and the housing body 114. A drivestub 117 a of the rotor 106 extends through the drive end plate 116 a tocommunicate mechanical movement with the companion device 104 a.

The end plates 116 a, 118 a carry bearings 122 that receive and supportthe rotor 106 to rotate about a rotational axis in the stator 108. Thebearings 122 can be a number of different possible types of bearings,and the number and types of bearings carried by the drive end plate 116a can be different from the number and types of bearing carried by thenon-drive end plate 118 a. The bearings 122 can include one or more ofjournal bearings (e.g., a tilt-pad journal bearing and/or other type),magnetic bearings (e.g., such as that described in U.S. Pat. No.6,700,258, U.S. Pat. No. 6,727,617, U.S. Patent Publication No.2002/0175578 and/or other type), hybrid magnetic bearings, ball bearingsand/or other types of bearing. One or more of the bearings 122 is athrust bearing (e.g., a tilt-pad thrust pad and/or other type). Incertain instances, non-drive end plate 118 a includes at least one axialor thrust bearing to axially retain the rotor 106 relative to thehousing 110 a and at least one radial bearing to provide radial supportto the rotor 106 relative to the housing 110 a, and the drive end plate116 a includes at least one radial bearing to provide radial support tothe rotor 106 relative to housing 110 a.

The stator 108 is generally cylindrical and the outer diameter thereofis closely received in the inner diameter of the housing 110 a tosupport the stator 108 relative to the housing 110 a. The outer diameterof the stator 108 may be keyed (using a protruding male key received ina female receptacle), bolted and/or otherwise secured to the innerdiameter of the housing 110 a to rotationally affix the stator 108relative to the housing 110 a. In certain instances, the stator 108 isaxially retained with end rings 126 that are bolted and/or otherwiseaffixed to the housing 110 a. One or more penetrators 128 (one shown forsimplicity of illustration) are provided through and sealed orsubstantially sealed with the housing 110 a to communicate fluid and/orelectrical power into the interior thereof. In certain instances, forexample in connection with a three phase electric machine 102 a, atleast three penetrators 128 are provided to conduct electricalconductors from a power electronics system (i.e., control system for theelectric machine) to the windings of the stator 108. Another penetrator128 may be provided that includes a conduit coupled to a supply heattransfer fluid to replenish any heat transfer fluid leaked from thehousing 110 a.

The non-drive end of the rotor 106 carries a fluid circulation pump 130that circulates the heat transfer fluid in the housing 110 a and throughan external heat exchanger 132. The pump 130 is coupled to the non-driveend of the rotor 106 to rotate with the rotor 106. The pump 130 can be anumber of different types of pumps, including a shrouded or unshroudedcentrifugal impeller pump, radial impeller pump, rotary vane pump, gearpump, screw pump, lobe pump and/or other type of pump. In certaininstances, the external heat exchanger 132 includes a continuous conduithelically coiled around the exterior of the housing 110 a. The externalheat exchanger has an outlet proximate the drive end of the electricmachine 102 a and an inlet proximate the pump 130. The pump 130 pumpsheat transfer fluid through ports 134 in the non-drive end plate 118 ainto the external heat exchanger 132. The fluid flows toward the driveend of the electric machine 102 a over the stator 108 and through thegap between the stator 108 and the rotor 106 and through gaps betweenthe stator 108 and the housing 110 a. In instances where the heattransfer fluid is cooler than the stator 108 and/or rotor 106, the fluidextracts heat from (i.e., cools) the stator 108 and/or rotor 106. Insome instances, when the shaft-driven circulation pump is mounted on thedrive end, the fluid at the drive end of the electric machine 102 aflows into the heat exchanger 132, is cooled as it is circulated throughthe helical coil and is returned to the non-drive end of the electricmachine 102 a over the stator 108 and through the gap between the stator108 and the rotor 106 and through axial gaps between the stator 108 andthe housing 110 a, and back to the pump 130 to repeat circulation. Inother instances, the fluid circulation gaps between the stator 108 andthe housing 110 a can be omitted. In instances where the electricmachine system 100 a is subsea, seawater helps cool the heat transferfluid circulated through the helical coil of the heat exchanger 132.Although shown as cooling the heat transfer fluid from within thehousing 110 a, the external heat exchanger 132 could additionally oralternatively receive and cool process fluids being acted upon by thecompanion device. Additionally, as described below the heat transferfluid in the housing 110 a and the process fluids can be one in thesame. In certain instances, the heat exchanger 132 could be used forcooling fluids from within the housing 110 a and an additional externalheat exchanger (not shown) can be provided about the housing 110 a toreceive and cool process fluids being acted upon by the companiondevice.

Although the pump companion device 104 a can be a number of differenttypes of pumps, FIG. 1B depicts a multistage centrifugal pump. Eightcentrifugal impellers 140 a are depicted arranged on central drive shaft142 a of the pump companion device 104 a. In other instances fewer ormore impellers can be provided. The drive shaft 142 a is shown coupledto the drive stub 117 a of rotor 106 by a drive coupling 144. Althoughdrive coupling 144 is shown as having two female ends that internallyreceive male ends of the drive stub 117 a and drive shaft 142 a, inother instances the drive coupling 144 can be a male coupling receivedinto female receptacles provided in the drive stub 117 a and the driveshaft 142 a. In certain instances, the manner of coupling the drive stub117 a and the drive shaft 142 a can include a combination of both maleand female drive coupling configurations and/or other configurations. Incertain instances, the drive shaft 142 a could be integral with therotor 106 (i.e., constructed as unitary part with the rotor 106, havingno coupling, gear box, screw thread or other mechanical connection). Thedrive shaft 142 a is supported on bearings 122 carried in a pump body146 a secured to the companion machine housing 148. As above, thebearings 122 can be a number of different possible types of bearings,and the number and types of bearings can be different at differentlocations along the drive shaft 142 a. The bearings 122 can include oneor more of journal bearings (e.g., a tilt-pad journal bearing and/orother type), magnetic bearings, hybrid magnetic bearings, ball bearingsand/or other types of bearing. One or more of the bearings 122 is athrust bearing (e.g., a tilt-pad thrust pad and/or other type). Incertain instances, drive end of the drive shaft 142 a (nearest drivecoupling 144) includes at least one axial or thrust bearing to axiallyretain the drive shaft 142 a relative to the pump body 146 a and atleast one radial bearing to provide radial support to the drive shaft142 a relative to the companion machine housing 148, and the non-driveend of the drive shaft 142 a includes at least one radial bearing toprovide radial support to the drive shaft 142 a relative to thecompanion machine housing 148. A seal 120 may be provided about thedrive shaft 142 a to seal or substantially seal against flow of fluidsfrom the centrifugal impellers 140 a towards the electric machine 102 a.

The companion machine housing 148 includes an inlet 150 through whichthe process fluid being pumped is communicated to the centrifugalimpellers 140 a. Rotating the centrifugal impellers 140 a pumps thefluid towards an outlet 152 of the companion machine housing 148. Inother implementations, the fluid flow may be reversed such that thecentrifugal impellers 140 a are adapted to produce a fluid flow from theoutlet 152 through the machine housing 148 and out through the inlet150.

In operation of the electric machine system 100 a, three phase ACelectric current is provided to the stator 108 of the electric machine102 a via the penetrators 128. The electrical current energizes windingsof the stator 108, and causes the rotor 106 to rotate. Rotating therotor 106 drives the drive shaft 142 a of the pump companion device 104a and pumps process fluid from the inlet 150 to the outlet 152. Rotatingthe rotor 106 also drives the fluid circulation pump 130 to pump fluidfrom non-drive end of the electric machine 102 a into the heat exchanger132, towards the drive end, over the stator 108 and through the gapbetween the stator 108 and the rotor 106, towards the non-drive end ofthe electric machine 102 a. Fluid proximate the non-drive end of theelectric machine 102 a flows into the heat exchanger 132 and is cooledas it passes through the helical coil of the heat exchanger 132 to driveend of the electric machine 102 a. Depending on the configuration of theshaft-driven fluid circulation pump, fluid can alternatively flow in thereverse direction (i.e., through the heat exchanger 132 toward thenon-drive end).

FIG. 1C depicts an example electric machine system 100 b where thecompanion device is a compressor 104 b. In FIG. 1C, the example electricmachine system 100 b includes two compressor companion devices 104 barranged on opposing ends of the electric machine 102 b. In otherinstances, fewer or more compressor companion devices 104 b can beprovided. In certain instances, two or more pump companion devices 104 acould be provided on the same side of the electric machine 102 a. Theexample electric machine system 100 b is configured for subseaoperation, submerged in the open sea (i.e., outside of a well). In otherwords, the example electric machine system 100 b is a subsea compressorsystem.

In general, the configuration of the electric machine system 100 b issimilar to that of the electric machine system 100 a discussed above.FIG. 1C shows the system 100 b configured for a cartridge typeinstallation/removal of the electric machine 102. To this end, all or amajority of the electric machine 102, including the stator 108 and therotor 106, is carried in an intermediate housing 115 that is received bythe housing 110 b. The intermediate housing 115 carrying electricmachine 102 components can be installed into or removed from the mainhousing 110 b as a unit or cartridge. The cartridge typeinstallation/removal simplifies service or replacement of the electricmachine 102, because the electric machine 102 need not beassembled/disassembled piece by piece into the main housing 110 b.Moreover, the electric machine 102 can be assembled into theintermediate housing 115 and tested prior to installation into the mainhousing 110 b.

Also notable, the interior of the housing 110 b is in communication withthe process fluids on which the compressor companion devices 104 b areoperating. Thus, the components of the electric machine are exposed tothe process fluids during operation of the electric machine system 100b. The process fluids are under pressure, because they have beencompressed by the compressor companion devices 104 b. In certaininstances, the process fluids are above the ambient pressure about theexterior of the electric machine system 100 b by an amount substantiallygreater than the incidental pressure incurred in circulating the processfluids through the electric machine system 100 b. In certain instances,communication is established by omitting a seal or providing animperfect seal about the drive shaft 142 b of the compressor companiondevice 104 b and/or providing other fluid communication paths from thecompressor companion device 104 b. The end plates 116 b, 118 b may beadditionally provided with ports 154 to facilitate communication ofprocess fluids into the gap between the rotor 106 and stator 108. Theelectric machine 102 b may also be provided without an integrated fluidcirculation pump 130.

In certain instances, the fluids used in operation of the electricmachine, including heat exchange fluids and other process fluids, cancontain constituents that may be corrosive, reactive and/or otherwiseharmful to one or more of the components of the electric machine 102 b.As described in more detail below, the rotor 106 and stator 108 may befortified against exposure to the process fluids. In certain instances,as described in more detail below, the rotor 106 and/or stator 108 maybe sealed against exposure to the process fluids and/or coated withprotective coatings.

Although the compressor companion device 104 b can be a number ofdifferent types of compressors, FIG. 1C depicts multistage centrifugalcompressors. Eight centrifugal impellers 140 b are depicted arranged oncentral drive shaft 142 b of the compressor companion device 104 b. Inother instances fewer or more impellers can be provided. As above, thedrive shaft 142 b is shown coupled to the drive end of rotor 106 by adrive coupling 144. In other instances, the drive shaft 142 b could beintegral with the rotor 106 (i.e., constructed as unitary part with therotor 106, having no coupling, gear box, screw thread or othermechanical connection).

FIG. 1C depicts an electric machine system 100 b incorporating magneticbearings 122. In certain instances, one end of the rotor 106 may besupported by an axial and radial magnetic bearing 122 carried in the endplate 118 b and the other end of the rotor 106 supported by a radialmagnetic bearing 122 carried in end plate 116 b. Additional conventionalbearings, for example cartridge ball bearings and/or another type, maybe provided to provide secondary and/or contingency support the rotor106. The companion devices 104 b can also be provided with magneticbearings 122 carried in the compressor body 146 b.

In operation of the electric machine system 100 b, three phase ACelectric current is provided to the stator 108 of the electric machine102 b via the penetrators. The electric current energizes windings ofthe stator 108, and causes the rotor 106 to rotate. Rotating the rotor106 drives the drive shaft 142 b of the compressor companion devices 104b and compresses process fluid from the inlet 150 to the outlet 152. Aportion of the process fluids is communicated with the interior ofhousing 110 b, causing process fluid to circulate over the stator 108and through the gap between the stator 108 and the rotor 106. Anadditional flow of fluid may be provided through the heat exchanger 132to be cooled as it passes through the helical coil of the heat exchanger132.

FIG. 2A depicts a cross-sectional view of an example rotor 200 for usein an electric machine system, such as a motor and/or a generator. Rotor200 could be used as rotor 106 described above. Additionally,implementations of the rotor 200 can be adapted for subsea operationand/or operation in corrosive environments. In certain instances,portions of the rotor 200 and rotor components can be coated or treatedfor corrosive resistance with Inconel, epoxy, polyetheretherketones(PEEK), ethylene chlorotrifluoroethylene copolymer and/or othertreatments. The rotor 200 can include rotor core having a rotor hub 202and rotor shaft 206. The rotor hub 202 is adapted to support permanentmagnets 204 positioned so as to magnetically interact with a statorprovided in the electric machine system. The magnets 204 can be bondedor otherwise connected to the rotor hub 202. High energy permanentmagnets 204 can be used, for example neodymium-iron-boron based, orsamarium-cobalt based magnets. In certain instances, the permanentmagnets 204 are bonded to the rotor hub 202. A rotor shaft 206 can beprovided, forming a rotational axis of the rotor 200. The rotor shaft206 extends axially from both ends of the rotor hub 202. The rotor shaft206 may be constructed as a single piece or modularly from a pluralityof shaft segments. In certain instances, the rotor shaft 206 can behollow, including the rotor hub, to promote rotor cooling or tofacilitate flow of fluid through the electric machine. The rotor 200 canfurther include one or more cooling passages 217 through the interiorthereof to communicate fluid through the interior of the rotor. In FIG.2A, a central passage 217 through center of rotor, entering oncircumferential surface of the rotor hub 202, is shown.

A rotor sleeve 212 can serve to enclose the outer surface of the entirerotor 200 or portions of the rotor 200, such as the rotor hub 202 andmagnets 204. The rotor sleeve 212 can be manufactured from material thatallows the sleeve to protect rotor components as well as providestructural support to rotor components, such as the rotor hub 202. Incertain instances, the rotor sleeve 212 can be constructed from a fiberreinforced composite, such as a carbon fiber composite, aramid fibercomposite (e.g., Kevlar a registered trademark of I.E. Dupont DeNemours), or fiber glass composite, a metal (e.g., Inconel, stainlesssteel, MP35N a registered trademark of SPS Technologies, Inc. and/orother metal), and/or other material. For instance, a sleeve covering 212can serve to provide radial support for the rotor hub 202 and magnets204 positioned thereon, preventing loosening or detachment of magnets204 from the rotor hub 202 during operation of the rotor 200 at highrotational speeds.

In certain instances, the sleeve 212 can also serve to insulate therotor 200 and rotor components from outside elements. For example, inrotors adapted for subsea and/or exposure to corrosive environmentsoperation, the sleeve 212 can be adapted to be air- or water-tight, inorder to seal the rotor components. For example, the electric machinesystem in which the rotor 200 is disposed may contain heat transferfluid, process fluids, and/or other fluids harmful to the rotor 200. Thesleeve 212 may cover and isolate those portions of the rotor 200sensitive to corrosion or otherwise adverse to contact with the fluid.

In certain instances, the rotor 200 may incorporate rotor elements andtechniques for mounting the rotor sleeve 212 to the rotor 200 so as toseal at least the rotor hub 202. As shown in the example of FIG. 2B,rotor 200 can include end rings 214 positioned at one or both ends ofthe rotor hub 202 and mounted coaxially on the rotor shaft 206. In thisexample, the end ring 214 is bonded or otherwise attached to the rotor200 so that the inner surface of the end ring 214 abuts the end of therotor hub 202, extending radially so as to provide axial support tomagnets 204 positioned on the rotor hub 202. The end rings 214 arepositioned at each end of the rotor hub 202. The end ring 214 can be ofmetallic material (e.g., Inconel, MP35N and/or other material). Incertain instances, the material can be selected for its ferromagneticproperties as well, so as to enhance or avoid interference with theelectromagnetic function of the magnetic rotor hub 202. Additionally,certain instances of the end ring 214 may be constructed so as to makethe end ring corrosion-resistant, for example, through galvanization oranodization of the end ring material. In other instances, the end rings214 can be built into or integrated into the rotor hub 202 itself. Forexample, a rotor hub 202 may be provided with an inset for mounting themagnets, resulting in the end sections of the hub having a largerdiameter than the inset.

A ledge 217 can be provided circumferentially on the outside diameter ofthe end ring 214. The ledge 217 serves as a landing platform for thepositioning of an end treatment strip 220 around the outside diameter ofthe end ring 214, the end treatment strip 220 forming a cylinder or ahoop. In certain instances, the outer diameter of the thin end treatmentstrip 220 is equal or approximately equal to the diameter of the rotorhub 202, including the magnets 204 mounted thereon. The end treatmentstrip 220 can be a composite material capable of bonding to the sleeve212. In certain instances, the end treatment strip 220 and sleeve 212are constructed from similar materials, such as pre-impregnated carbonfiber or other material. A circumferential groove 221 can also beprovided on the ledge 217 of the end ring 214, in order to provide for aseal 222 (e.g., an o-ring, gasket and/or other seal) to be positioned onthe ledge surface 217. The seal 222 seals or substantially seals betweenthe end ring 214 and the end treatment strip 220 wrapped around the endring's ledge 217. Of note, in certain instances, the circumferentialgroove 221 can be machined onto the end rings 214 before and/or afterthe end rings 214 are installed to the rotor 200 (as discussed below).

In one example, the sleeve 212 can be sealed to the rotor 200 by slidingand/or threading the end rings 214 onto the shaft 206 so as to abut theends of the rotor hub 202. In certain instances, a seal (e.g., o-ring,gasket and/or other seal) and/or sealant (e.g. thread sealant, sealantapplied to the juncture between the shaft 206 and end rings 214, and/orother sealant) can be provided between the shaft 206 and the end rings214. The seal 222 can be positioned in the end ring 214 before or afterpositioning and connecting the end ring 214 to the shaft 206. In aninstance where the end rings 214 are threaded onto the shaft 206, therespective threads of the end rings 214 can be oriented so that the endrings 214 are tightened to the shaft 206 when the rotor 200 is rotatedin normal operation. In some instances, the end rings 214 canadditionally be affixed to the rotor hub 202 with an adhesive.

After rigidly connecting the end ring 214 to the shaft 206 (e.g., bythreading, welding and/or otherwise), the end treatment strip 220 ispositioned on the outside diameter of the end ring 214 on the ledge 217.The end treatment strip 220 may then be wound onto the ledge 217, toposition the strip 220 on the end ring 214, or may simply be slippedover the end ring 214 into position on the ledge 217. With the end rings214, seals 222, and end treatment strips 220 in place, the constructionof the sleeve 212 can be completed. Winding or otherwise securelywrapping the sleeve 212 onto the rotor hub 202 and on top of the endtreatment strip 220 can press the end treatment strip 220 radially downonto the ledge surface 217, causing the strip 220 to shrink tightly ontothe end ring 214. This pressure, in turn, compresses the seal 222 intothe groove 221 to form a seal between the strip 220 and the end ring214. As the sleeve 212 is wound onto the rotor 200 the sleeve 212 isbonded to the strip 220. This bonding extends the seal between the strip220 and end ring 214 to the sleeve 212, thereby sealing the rotor hub202 covered by sleeve 212. In certain instances, clamps may be employedto secure the strip 220 to the end ring 214 while the sleeve is wrappedto the rotor 200 and bonded to the strip 220. Additionally, the bondingof the strip 220 to the sleeve 212 can occur at an elevated temperature,to allow for a bond that will be less temperature sensitive.

Alternative techniques can be employed to seal the sleeve to the rotorassembly. For example, in some implementations, the end treatment strips220, the seal 222, and seal grove 221 may be omitted. In some instances,the sleeve may be securely wound onto the rotor hub 202 and thecircumferential surfaces of the end rings 214. The sleeve 212 may befabricated from carbon fiber impregnated with thermoplastic materialsuch as polyetheretherketone (PEEK). Thermoplastic material, such asPEEK, may also be applied to or pre-coated on the outer diameter of theend rings 214 prior to having the sleeve 212 wound on the hub assembly.Where grinding of the rotor assembly may be required, pre-coated endrings 214 may be provided with sufficient material so that a coatingformed from PEEK (or other material), for example, remains on the endrings 214 following grinding and before the sleeve 212 is wound overboth the end rings 214 and rotor hub assembly. With the sleeve incontact with the PEEK-coated end rings, heat or pressure may be appliedto bond the sleeve to the end ring, forming a seal with the PEEK at eachend of the sleeve 212, thereby isolating the rotor hub, magnet segments,and other components covered by the sleeve from contact with potentiallyhazardous external fluids and/or other materials.

After the sleeve 212 is wrapped on the rotor 220 secondary end rings 215may be slid and/or threaded onto the shaft 206 so as to abut the endrings 214. The secondary end rings 215 have a diameter substantiallyequal to the sleeve 212 diameter, and serve to protect the outer surfaceof the sleeve 212 and/or to provide a location for rotor balancing(either by material removal or addition). In certain instances, a seal(e.g., o-ring, gasket and/or other seal) and/or sealant (e.g. threadsealant, sealant applied to the juncture between the shaft 206 andsecondary end rings 215, and/or other sealant) can be provided betweenthe shaft 206 and the secondary end rings 215. Additionally, thejuncture between the secondary end rings 215 and the end rings 214 canbe filed with resin and/or adhesive (thus, adhering the secondary endrings 215 to the end rings 214 and filling). In an instance where thesecondary end rings 215 are threaded onto the shaft 206, the respectivethreads of the secondary end rings 215 can be oriented so that thesecondary end rings 215 are tightened to the shaft 206 when the rotor200 is rotated in normal operation. In certain instances, the outwardfacing edges of the secondary end rings 215 can be rounded or the rings'outer surface may be conical (with the smaller diameter facing outward)to facilitate fluid flow over the secondary end rings 215.

Some implementations may employ additional measures to protect the endsof the sleeve 212 in addition to or in lieu of the secondary end rings215. For example, tubular bands, constructed of material more resistantto wear and other damage than the composite sleeve 212 (e.g.,non-magnetic metal, ceramic, polymer and/or other material), may bepositioned at each end of the rotor hub, concentrically atop the sleeve212. Consequently, the tubular bands may cover the ends of the sleeve,thereby protecting the ends of the sleeve from erosion, abrasion, orother damage that may occur during operation of the rotor 200. Inanother implementation, illustrated in FIGS. 2C and 2D, a tubular bandmay be replaced with a thin, non-magnetic, metal alloy tape 223 (e.g.,nickel alloy (e.g., Inconel), non-magnetic stainless steel, titaniumand/or other metal) wrapped around the outer surface of the rotor sleeve212 and bonded to end rings (not shown) positioned on the rotor shaft206 to form a sleeve 229. In some instances the metal can be corrosionresistant. In some implementations, a insulating coating and/or surfacetreatment may be applied to the tape 223 to inhibit currents fromcirculating between adjacent laps of the tape 223. Some examples ofcoating and/or surface treatment include oxidation, anodization,phosphate/chromate/silicate coating (e.g., American Society for Testingand Materials (ASTM) A976 C-4 and/or C-5) and/or other coatings. In someimplementations, the sleeve 229 may extend axially beyond the edges ofthe rotor sleeve 212.

In one implementation, a first end of a piece of tape 223 may be bondedto an end ring adjacent to a first sleeve end 225. The tape 223 may bebonded to the end ring using a laser weld, resistance weld, TIG weld,chemical bond, or any bonding method. The tape 223 may be wound on topof the rotor sleeve with adequate tension so as to cover the sleeve endsand maintain positive pressure between the tape 223 and the rotor sleeve212 in all operating conditions of the rotor 200. The resulting tapewinding 223 may be laid in butt laps across the outer surface of therotor sleeve, resulting in a smooth surface that minimizes the thicknessof the tape wrapping 223. Thin alloy tape wrappings 223 may, among otheradvantages, minimize parasitic mass as well as parasitic currentsappearing in the metallic tape as a result of the magnetic field of therotor 200 or corresponding electric machine. Other implementations mayemploy other winding techniques as well as various tape material forreinforcing and protecting the rotor sleeve. Upon winding the tapeacross the rotor hub 202 to cover the second end of the sleeve 227, thesecond end of the piece of tape 223 may be bonded to the opposite endring. In some instances, for example in a butt lap winding, excess tapemay result at the edges of end rings. The excess tape may be trimmedflush with the end ring faces to complete the tape winding 223.

FIG. 2E is a detailed cut-away cross-sectional view of an example sleeve212. The sleeve 212 can be manufactured or constructed of any materialpossessing the structural, resistive, and/or chemical properties desiredfor the particular rotor implementation, for example a fiber-reinforcedcomposite. The sleeve 212 can serve a number of functions. For example,in subsea and/or corrosive environment rotor implementations, the sleeve212 can be constructed of composite material capable of providingstructural support and corrosion protection for the rotor hub, as wellas sealing the rotor hub from exposure to foreign elements. Heating ofthe rotor 200 can result in thermal expansion of one or more of therotor elements or sleeve. Where heating is uneven across the rotor, somesections of the rotor and rotor sleeve can expand differentiallyrelative to other sections. Differential thermal expansion can result indifferential, and potentially damaging, stresses on the sleeve 212.Stress can arise due to differential expansion of the sleeve itself orfrom differential expansion of the underlying rotor structure.Accordingly, the below described sleeve configurations can, among otherbenefits, more uniformly control and/or accommodate thermal expansion,both of the sleeve and the rotor itself.

In some instances of rotor sleeve 212, a fiber-reinforced compositesleeve material, such as carbon fiber, can be employed. In certaininstances, as illustrated in the example of FIG. 2E, the sleeve may bemulti-layered. FIG. 2E shows a multi-layer fiber-reinforced compositesleeve wrapping 212. The top layer 224 (or, in certain instances,layers) are cosmetic layers. These layers may possess functionalcharacteristics as well. For example, to achieve strength and rigidityas well as control differential thermal expansion in one or multipledirections, the layers can have fibers oriented predominantly or all inthe same direction (e.g. maximum strength in one direction) or differentorientations (strength in multiple directions).

In certain instances, intermediate layer 226 can be a first, primarilyaxially-oriented carbon fiber composite layer layered beneath thecosmetic layer 224 (i.e., nearer to the outer circumferential surface ofrotor 200). The layer 226 can be made of pre-impregnated carbon fibercomposite sheet capable of providing very strong axial support as wellas provide corrosion and leakage protection. Layer 228, positionedbeneath layer 226, can be one or more carbon fiber composite layers withprimarily circumferentially-oriented pre-impregnated carbon fiber tape.Layers with circumferentially-oriented carbon fiber, such as layer 228,do not provide substantial axial strength, instead providingcircumferential strength. Additionally, circumferentially-orientedcarbon fiber layers, while useful in controlling radial thermalexpansion, are less effective at useful for limiting axial expansion.Layer 230 is a bottom, primarily axially-oriented carbon fiber layer andin certain instances is made from pre-impregnated carbon fiber compositesheet. Axially-oriented layers, such as layer 230, can remedy thestructural deficiencies of circumferentially-oriented carbon fiberlayers, both in terms of structural and thermal expansion support.Accordingly, in some instances, intermediate 226 and bottom layers 230can have substantially axial reinforced composite fibers, the layer 228having substantially circumferential reinforced composite fibers.

Layer 230 can be wrapped so as to directly contact the rotor 200, rotorhub 202, rotor hub magnets 204, and/or end rings 214, covering all or aportion of the rotor 200. In certain instances, additional layers can beprovided between layer 230 and the rotor 200. Additional layers may alsobe provided between layers 224, 226, 228, and 230. Indeed, certaininstances may make use of repeated layering of layers 224, 226, 228, 230in similar or different orientations and orders. Although discussedabove with respect to axially-oriented and circumferentially-orientedlayers, the orientations of one or more of the layers 224, 226, 228, 230could be oriented in non-axial and/or non-circumferential directions.For example, one or more of the layers 224, 226, 228, 230 could beoriented at 45 degrees, 30 degrees and/or another angle relative to theaxial direction. Indeed, in some instances, fibers in a fiber-reinforcedcomposite, need not be oriented in the same direction. Accordingly, insome instances, fiber-reinforced composites can be selected for theaxial and circumferential support that have fibers primarily in one ofthe axial or circumferential direction. The layer, in such an instance,can have a greater density of fibers oriented on one orientation ordimension, than in another dimension.

The material forming the layers of a multi-layered sleeve 212 need notbe uniform. In certain instances, the one or more layer materials may beselected so as to minimize stress on the rotor hub 202, magnets 204, aswell as the surrounding sleeve 212 due to thermal expansion duringoperation. One technique for minimizing these stresses is to build thesleeve 212 so that the sleeve 212 expands axially with the interiorrotor components at the rotor's 200 operating temperature.

The rotor 200, rotor components, and sleeve layers expand according tothe coefficient of thermal expansion (CTE) of materials used in therotor and sleeve. Accordingly, rotor sleeve 212 materials can beselected and/or engineered to have CTEs similar to the CTEs of theportion of the rotor 200 or rotor elements to be covered by the rotorsleeve 212. For example, in a fiber-reinforced composite rotor sleeve,the fiber and/or resin employed to form the rotor sleeve, can beselected so as to result in a composite sleeve material with a CTE equalor substantially equal to, complimenting, or otherwise matched to theCTE of the rotor shaft 206, rotor hub 202, and/or magnet 204 material.Matching CTE can, among other benefits, allow the sleeve 212 to expandwith the expansion of the rotor components wrapped in the sleeve 212.

In some instances, in order to achieve a desired CTE in a sleeve layeror rotor component, material used in the sleeve or rotor component canbe doped with other material having a higher or lower CTE so as toaffect the net CTE of the resulting sleeve or rotor component. Forinstance, the resin of a carbon fiber sleeve layer could be doped sothat the CTE of the carbon fiber sleeve layer matches the CTE of rotorcomponents covered by the sleeve, for example neodymium-iron-boronbased, or samarium-cobalt based magnets mounted on the rotor hub 202.Additionally, the density of fibers used in a fiber-reinforced sleevecan also be adjusted so as to engineer the net CTE of the sleeve orsleeve layer. In certain instances, one or more layers, includingaxially oriented, circumferentially oriented and/or other orientedlayers, may be selected with varying CTEs so as to engineer a sleevehaving a net CTE matched to the relevant portions of the rotor 200 to becovered by the sleeve 212. In certain instances, non-CTE-matched sleevelayers can be provided in addition to CTE-matched sleeve layers in thesleeve 212. For example, sleeve layers closest to the rotor hub 202surface may be selected with CTE matched to the CTE of the rotor hub orrotor hub components, while outer sleeve layer material is selectedbased on other considerations, such as structural support, punctureresistance, or corrosion resistance.

In some implementations, the CTE of the rotor 200 to be covered by thesleeve 212, can vary across the rotor 200, depending, for example, onthe rotor elements employed in and on the rotor 200. Rotors havingdifferential CTE may result in differential thermal expansion in therotor as well as the sleeve covering the rotor. Accordingly, in someimplementations, rotor sleeves can be engineered to have differentialCTE, for example by differential doping across the length of the sleeve,to correspond with varying CTEs in the rotor portions to be covered.

FIGS. 2F and 2G illustrate another implementation of an example rotorsleeve 212. FIG. 2F shows a detailed cross-sectional view of amulti-layered rotor sleeve 212. FIG. 2G is a detailed perspective viewof the sleeve shown in FIG. 2F. A set of outer layers 232, 234 can beprovided in the sleeve 212 together with a set of segmented layers 236,238, 239, 240. The outer layers 232, 234 can include one or morecomposite layers, including axially, circumferentially and/or otherwiseoriented layers. The segmented layers 236, 238, 239, 240 are distinct,hoop-like layers. A segmented layer can expand and contract independentfrom other segmented layers. Where differential temperatures makedifferential expansion or contraction likely, segmented layers 236, 238,239, 240 can expand and contract in these regions of differentialtemperature and propagate less of the associated forces from expansionor contraction to other segmented layers, outer layers 232, 234, or thesleeve 212 generally.

In certain instances, the segmented layers 236, 238, 239, 240 can assumewidths and positions in the sleeve 212 coordinating with circumferentialsegmentation of magnets 204 a, 204 b, 204 c, 204 d on the rotor 200. Forexample, as shown in FIG. 2F, in rotors having circumferentiallysegmented magnets 204, the segmented layers 236, 238, 239, 240 arepositioned to align with the circumferential segmentation of one or moreof the magnets 204 a, 204 b, 204 c, 204 d so that each segmented layeris aligned with one or more circumferential rows of magnets. This canallow for the expansion and contraction of each segmented layer 236,238, 239, 240 to be influenced by the thermal expansion and contractionof magnet row 204 a, 204 b, 204 c, 204 d positioned beneath it. Whilethe example of FIGS. 2F and 2G show segmented layers with axial widthscorresponding to a single magnet row, segmented layers can correspondwith and cover more than one row of magnet segments. Additionally,segmented layers 236, 238, 239, 240 can be fiber-reinforced compositehoops having primarily circumferentially-oriented fiber, so as toprovide structural support to the magnet segments positioned beneath thehoop layer. In some instances, magnet segments may be subject to greaterthermal expansion and structural vulnerabilities (e.g., during rotationof the rotor at high speed), requiring additional radial support tolimit these liabilities.

In an illustrative example, the temperature at magnet 204 a may behigher than the temperature at magnet 204 c. The temperaturedifferential between magnet rows 204 a and 204 c can result in magnet204 a experiencing thermal expansion larger than that experienced atmagnet row 204 c. Accordingly, segmented layer 236 positioned inalignment with magnet row 204 a may expand more than segmented layer 239positioned in alignment with magnet row 204 c. Gaps may exist betweenthe segmented layers 236, 238, 239, 240 so that the expansion of onesegmented row does not interfere with another segmented layer.Additionally, expansion forces in layers 232, 234, positioned above thesegmented layer, resulting from differential thermal expansioncorresponding with one or more hoop segments, may be focused at or nearthe corresponding hoop segment, including the gap between the affectedhoop segments. For instance, in the above example, thermal expansionforces transmitted to layers 232, 234 may be focused at the gap betweenadjacent hoop segments 236 and 238; 238 and 239; and 239 and 240.

A segmented layer can also be accomplished using a unitary sleeve layer.For example, a sleeve layer can possess strength characteristics thatvary across the length of the sleeve layer. Variation in sleeve layerstrength can be aligned with elements, such as magnet segment rows, sothat areas of highest strength are aligned with areas of the rotorrequiring greatest reinforcement or more subject to differential thermalexpansion. For example, multiple layers of varying physicalcharacteristics could be grouped to form a sleeve with band-likestrength sections, with gaps between the sections exhibiting strength orthermal expansion characteristics different than the sectionsthemselves. One way this may be accomplished is by fabricating sleeveswith varied coefficients of thermal expansion (CTE). Additionally, incertain instances, the segmented layers 236, 238, 239, 240, or segmentedhoops, aligned with magnet segment rows 204 a, 204 b, 204 c, 204 d, maybe constructed of material with CTEs matched to the CTE of the magnet204 a, 204 b, 204 c, 204 d positioned beneath it.

While FIGS. 2A, 2F, and 2G show examples of a rotor hub 202 with magnets204 axially segmented (with segment boundaries formed in thecircumferential plane along the axial body of the rotor hub 202), themagnets 204 can also be implemented as single member magnets, extendingaxially across the length of the hub body 202. Additionally, magnets canbe segmented circumferentially (with segment boundaries formed in aradial-axial plane) as shown in 2E. Segmenting the magnets, however, canbe advantageous as certain magnets may be more affordable and easier toimplement as segmented pieces. Additionally, segmented magnets 204 canalter the electric and electromagnetic characteristics of the rotor andthereby be functionally desirable in some rotor applications.

FIGS. 2H-2P are cross-sectional views of example rotor hubs 202. Magnets204, of uniform or non-uniform strength, can be mounted directly to theouter surface of the rotor hub 202 and/or to the rotor hub 202 viaintermediate materials, for example, to electrically insulate themagnets 204 from the rotor hub 202, bond or improve bonding to the rotorhub 202, and/or other reasons. In certain instances, the intermediatematerial can include an adhesive (e.g., an acrylic adhesive and/or otheradhesives), electrically insulating tape, a solder material, a reactivenanofilm, and/or another material. In certain instances an interstitialfiller material is applied to the rotor 200 to fill spaces between themagnets 204 and/or the rotor hub 202. An example material, includesstainless steel putty (e.g., stainless steel putty made by ITW Devcon)and/or other materials. In certain instances, the rotor 200, prior toinstallation of the sleeve 212, can be dipped in or flooded with anepoxy resin to ensure all the gaps between the magnets 204, the rotorhub 202, and/or the end rings 214 are filled and further protect againstfluid ingression.

In certain instances interstitial filler material may be injected intothe rotor hub assembly while providing a vacuum within the hub assembly.For example, once magnet segments 204 have been mounted to the rotor hub202, the magnets 204 and rotor hub 202 may be enclosed in a disposablesleeve (e.g., a polymer bag and/or other sleeve), and the sleeve may besealed at both ends of the rotor hub assembly. The vacuum is operable toremove the air and/or other gases (“gases”) within the sleeve, includinggases residing in voids between the magnets 204 and/or the rotor hub202. A pre-catalyzed low-viscosity thermosetting resin may be introducedinto the disposable sleeve to penetrate the empty spaces in the rotorhub assembly. Upon curing of the resin, the disposable sleeve may beremoved. Thereafter, manufacture of the rotor may be resumed, includingwrapping a protective rotor sleeve 212 around the rotor hub assembly.

In some implementations, the rotor sleeve 212 itself may be used in lieuof the disposable sleeve of the previous example. Pluggable inlets maybe provided on each of the end rings 214, allowing a vacuum pump to beconnected to one end of the hub assembly and a high pressure pump to beconnected to the other end. The vacuum pump vacates air from the hubassembly, sealed by the sleeve 212. With air removed from the inside ofthe hub assembly, the high pressure pump may inject the resin into voidsin the hub assembly. The end ring inlets may be plugged and the resincured to seal the hub assembly interior. Subsequent manufacturingoperations may then be performed.

To facilitate filling the voids within the rotor hub assembly using thedescribed or other techniques, the hub and/or the magnet segments may beprovided with flow path channels to guide filler material into voidsbetween the hub 202 and the magnet segments 204. FIGS. 2Q-2R illustrateexamples of such features. For instance, FIG. 2Q shows a rotor hubassembly 201 including a rotor hub 202 with a plurality of magnetsegments 204 mounted on the hub 202. The magnet segments 204 are eachformed to take a geometry that results in flow path channels 258 beingformed when the magnet segments 204 are mounted to the hub 202. Thesechannels 258 may be aligned with those areas of the hub 202 and magnetsegments 204 where voids are likely to appear, such as areas betweenadjacent magnet segments 204. In some instances, as shown in FIG. 2R,additional grooves 260 may be provided on the hub 202, in lieu of or inaddition to the geometry of the magnet segments 204, to provide the flowpaths 258.

The end rings of the assembly may also be used to guide the flow offiller material. As shown in FIG. 2S, an interior face of an end ring214, to be set adjacent to the rotor hub, can be provided with anannular channel 262 operable to direct filler material around the rotorhub assembly and into voids or other flow path channels positionedaround the rotor hub. In some implementations, an inlet 264 incommunication with the channel 262 may be provided on the end ring 214.The inlet 264 may be used to couple one or more vacuum pumps orinjection pumps to the end ring 214 to deliver and direct fillermaterial into voids within the hub assembly.

The magnets' dimensions and orientation on the rotor hub 202 may serveto form substantially a cylinder of magnet segments around the hub 202.In some implementations, outer surfaces of the magnet segments mayrequire grinding once the magnetic segments are mounted to the hub 202.Grinding the outer surfaces of the magnetic segments may be used to formthe rotor hub 202 into a substantially uniform cylindrical outersurface. Additionally, while the magnets, once coupled to the rotor, mayform a uniform cylinder, individual magnet segments 204 a-t can vary inmagnetic field orientation and magnitude as well as weight in order toachieve the desired electromagnetic, rotational and inertial rotor hub202 profile.

FIG. 2H illustrates a cross-sectional view of one example rotor hubmagnet configuration. In this example, sixteen circumferentiallysegmented magnets 204 a-t are positioned around the circumference of therotor hub 202. The geometry of the individual magnet segments 204 a-tand the outer surface of the rotor hub 202 allow for the magnet segments204 a-t to be mounted directly to a rotor hub 202. As shown in FIG. 2H,the outer surface of the rotor hub 202 in certain instances may not beperfectly round, for example, the portion of the rotor hub 202 wheremagnet segments 204 a-t are mounted may be a regular polygon with anumber of equilateral sides equal to the number of magnet segments 204a-t to be mounted on the hub 202. FIG. 2H shows the outer surface of therotor hub 202 having sixteen flat surfaces, running the axial length ofthe rotor hub 202, against which corresponding flat surfaces of thesixteen magnet segments 204 a-t abut. The flat surfaces on the rotor hub202 and the magnet segments 204 a-t are normal to a radial lineemanating from the center of the hub 202.

The magnet segments 204 a-t can be arranged into a two poleconfiguration. For example, seven magnet segments 204 a-g with magneticfields directed substantially radially away from the center of the rotorhub 202 may serve as a base of a north pole of the rotor's magneticconfiguration. Seven other magnet segments 204 j-s can be positioned onthe other side of the rotor hub 202, each magnet segment 204 j-s havingmagnetic fields directed substantially radially toward the center of therotor hub 202 serving as a base for a south pole of the rotor's magneticconfiguration. A magnet segment 204 may be magnetized so that themagnetic field vector of the magnet segment is uniform. In other words,the magnetic field vector at any one point along a uniform magnetizedmagnet segment is parallel to the magnetic field vector at any otherpoint along the magnet segment, as illustrated in FIG. 2T. In certaininstances, the magnetic field vector at the center of the magnet segmentis radial. As discussed in more detail below, in other instances, themagnetic field vectors can be normal to radial or arcuate having thesame center as the rotor. Alternatively, as illustrated in FIG. 2U, amagnet segment 204 with a true radially-directed magnetic fieldpossesses a magnetic field with magnetic field direction vectors thatare each radial. In instances where the outer surface the magnet segmentis an arc in the round outer surface of a circular rotor, the magneticfield direction vectors can be normal to the outer surface 268 of themagnet segment. In uniform magnetic segments, the magnetic fielddirection vectors can be configured to all be perpendicular to themating flat surfaces of the magnet segment and rotor hub. In radialmagnetic segments, the magnetic field direction vector at the centerline of the magnetic segment can be configured to be perpendicular tothe mating flat surfaces of the magnet segment and rotor hub.

Returning to FIG. 2H, disposed between the two poles are interpolemagnet segments 204 h, 204 t. Interpole magnet segments 204 h, 204 t canbe provided to adjust the magnetic flux distribution of the rotor 200,transitioning the magnetic field between the two poles. In theimplementation pictured in FIG. 2H the interpole magnet segments 204 h,204 t possess geometries similar to the radial magnet segments 204 a-g,204 j-s, the interpole magnet segments having magnetic fields directednormal to these radial fields, or tangent to circumference of the rotor200.

The arrangement of permanent magnet segments on the rotor hub 202 canresult in a net magnetic pole center vector 270 for the rotor 200. Inthe example of FIG. 2H, the magnetic pole center has a direction vectorcomponent centered on magnet segment 204 d, the geometric center of therotor's north pole. The rotor illustrated in FIG. 2H has a regular polecenter. The pole center 270 of the rotor 200 illustrated in FIG. 2P isalso regular. As illustrated in FIG. 2P, the pole center vector 270 isaligned between magnet segments 204 b and 204 c, this interfacerepresenting the geometric center of the top pole in rotor 200. Wherethe magnetic pole center 270 is aligned with the geometric midpoint ofthe array of magnet segments establishing a north (or south) magneticpole, the pole center is regular. FIG. 2K, on the other hand,illustrates an example of a rotor with an irregular pole center 270. Thegeometric center of rotor 200 in FIG. 2K, is the arcuate midpoint ofmagnet segment 204 d. As illustrated, pole center 270 in FIG. 2K is notaligned with the geometric center of the rotor. Depending on the designof the stator, and the objectives for the electric machine, it can bedesirable to implement rotors with either a regular or irregular polecenter vector.

FIG. 2I illustrates a cross-sectional view of another rotor magnetconfiguration. The structural dimensions of the rotor magnetconfiguration of FIG. 2I can be substantially similar to the structuraldimensions of the rotor magnet configuration of FIG. 2H. Theconfigurations of FIGS. 2H and 2I can have the same number of magnetsegments, the magnet segments having substantially identical physicaldimensions. However, while FIG. 2H illustrates an example two-pole rotordesign, FIG. 2I illustrates an example four-pole design. The first poleof FIG. 2I includes magnet segments 204 a, 204 b, 204 c, the second poleincludes magnet segments 204 e, 204 f, 204 g, the third pole with magnetsegments 204 j, 204 k, 204 m, and the fourth pole with 204 p, 204 q, 204s. At least one interpole magnet segment 204 d, 204 h, 204 n, 204 t canbe provided for each pole in the configuration, the interpole magnetsegments 204 d, 204 h, 204 n, 204 t positioned between two adjacentpoles. Interpole magnet segments 204 d, 204 h, 204 n, 204 t can havemagnetic fields directed approximately normal to the radial fields ofthe remaining magnet segments. In certain instances, half of theinterpole magnet segments 204 h, 204 t can have magnetic fields directedin the clockwise direction, the other interpole magnet segments 204 d,204 n can have fields directed in the counter-clockwise directions.

While FIGS. 2H and 2I are each implemented with sixteen magnet segmentsper row (or sixteen hub facets and equivalently shaped magnet segments),other rotor designs employing permanent magnet segments may also beprovided. For example, more or fewer than sixteen facets can beemployed, including facets with varying geometries. For example,geometries can be employed, such as those described above in connectionwith FIGS. 2Q and 2R, providing flow path channels between adjacentmagnet segments. In some instances the outer surface of the magnetsegment can be flat, as opposed to round as in FIGS. 2H and 2I. Themagnet segment's interface with the rotor hub can also affect itsgeometry (as in the case of a facet, as shown, for example, in FIGS.2G-2R). Indeed, alternative configurations, numbers of facets, andgeometries can be employed as substitutes for other rotor designs withcomparable magnetic profiles. For example, a substitute for the two-polerotor illustrated in FIG. 2H can be achieved using only fourcircumferential magnet segments mounted to the rotor hub 202, asillustrated in FIG. 2J. Two pole magnet segments 204 w, 204 y can beemployed for the north and south poles of the rotor, with two,additional interpole magnet segments 204 x, 204 z disposed between themagnet segments 204 w, 204 y. Given that the pole segments 204 w, 204 yare the primary magnetic segments for the rotor 200, someimplementations, including the example illustrated in FIG. 2J, mayprovide for polar segments 204 w, 204 y with longer arcuate spans thanthe transitional interpole magnet segments 204 x, 204 z. Additionally,the outer surfaces of the magnet segments, when mounted on the rotor hub202, can form a cylindrical outer surface of the rotor 200, as alsoillustrated in the sixteen facet example of FIG. 2H. While the fourmagnet segment rotor of FIG. 2J has two poles, as in FIG. 2H, the FIG.2J rotor may have a magnetic profile and performance characteristicsdistinct from those of the sixteen facet rotor of FIG. 2H. Additionally,other configurations, employing the principles illustrated in theexamples of the FIGS. 2H and 2J, are within the scope of the disclosure,allowing several facet-based design options tailored to the economicsand performance considerations of the designer.

FIG. 2K is a cross-sectional view of yet another example two-pole magnetconfiguration. The two-pole magnet configuration example of FIG. 2K canemploy interpole magnet segments 204 h, 204 t utilizing split-interpoleconstruction. Each interpole magnet segment 204 h, 204 t can beconstructed of two separate magnet pieces 254, 256, bonded together toform a single magnet segment. Radial magnet segment piece 254 can be amagnet with a radially-oriented magnetic field. Magnet segment piece 254h belonging to interpole magnet segment 204 h can have a radial magneticfield directed away from the center of the rotor hub 202. Magnet segmentpiece 254 t belonging to interpole magnet segment 204 t can then have aradial magnetic field directed toward the center of the rotor hub 202.Normal magnet segment pieces 256 h, 256 t can be bonded to radial magnetsegment pieces 254 h, 254 t to form respective interpole magnet segments204 h, 204 t. Normal magnet piece 256 h, bonded to radial magnet piece254 h, can have a magnetic field directed normal to the radial magneticfield of piece 254 h, and oriented in a counter-clockwise direction.Normal magnet piece 256 t, bonded to radial piece 254 t, can have amagnetic field normal to the radial direction, the field of normal piece256 t oriented in the clockwise direction. Magnet pieces 254, 256 can beconstructed of the same or dissimilar magnetic materials. Magnet pieces254, 256 can be equal sizes, or alternatively, one magnet piece can belarger than the other. Selecting the materials of the magnet pieces 254,256 as well as the size of one piece relative the other can be done toengineer the magnetic characteristics of the interpole magnet segment204 h, 204 t, allowing rotor designers to refine the magneticcharacteristics of the interpole magnet segments 204 h, 204 t andthereby modify some magnetic flux characteristics of the rotor.

As shown in FIG. 2L, split-interpole magnet segment designs similar tothat described above with the example of FIG. 2K can also be employed inmagnet configurations with more than two poles. For example,split-interpole magnet segments 204 d, 204 h, 204 n, 204 t can beemployed in four-pole magnet configurations similar to, for example, thefour-pole magnet configuration described in FIG. 2I.

Rotor hub 202 magnet configurations can employ more than one interpolemagnet segment per pole. The rotor hub 202 examples illustrated in FIGS.2H-2I can form the base for building numerous, varied magnetconfigurations by mounting varied combinations of modular magnetsegments 204 a-t on the hub 202 with varying magnetic fieldorientations, magnetic material characteristics, and material densities.For example, the four-pole configuration example of FIG. 2I can bemodified by replacing radially-oriented magnet segments 204 a, 204 c,204 e, 204 g, 204 j, 204 m, 204 p, 204 s with non-radial magnetsegments, as shown in FIG. 2M, so that adjacent magnet segments 204 a-c,204 e-g, 204 j-m, 204 p-s possess parallel-oriented magnetic fields. Asshown in FIG. 2N, other implementations may alter the four-poleconfiguration of FIG. 2I, exchanging the normal-oriented interpolemagnet segments of FIG. 2I with interpole magnet segments 204 d, 204 h,204 n, 204 t possessing magnetic fields oriented with directionalvectors approximating the vector sum of the two magnet segment pieces ofthe split-interpole magnet segments of FIG. 2L.

Yet another example illustrating the broad compatibility of the rotorhub 202 and modular magnet segments 204 a-t, is shown in FIG. 2O. Atwo-pole magnetic configuration with uniform magnetization can beconstructed with magnet segments 204 a-t constructed so that themagnetic field of each magnet segment is oriented parallel to and in thesame direction as every other magnet segment's magnetic field when allmagnet segments 204 a-t are mounted on the rotor hub 202. Depending onthe configuration of the cooperating stator in the electric machine,substantially uniform rotor magnetizations, such as the two pole designof FIG. 2O, can provide more efficient electromagnetic power conversion

In addition to the two pole, uniform magnetization design of FIG. 2O,four pole uniform rotor designs are attainable using the facet-basedapproach described. For example, in FIG. 2P, a sixteen facet rotor isprovided. In the example of FIG. 2P, the first pole includes magnetsegments 204 a, 204 b, 204 c, and 204 d. The magnetic field directionvectors of each of the magnet segments in this first pole, when mountedto the rotor hub 202 are parallel to the magnetic field directionvectors of the others magnet segments in the pole. Such is also the casein the other three poles of the rotor example of FIG. 2P. A second polecan include magnet segments 204 j, 204 k, 204 l, and 204 m. The secondpole magnet segments in this example, have magnetic field directionvectors parallel to the magnetic field direction vectors of the firstpole, but oriented in the opposite direction to the first pole magnetsegments' magnetic fields. Third and fourth poles are provided, eachwith magnetic field direction vectors orthogonal to the magnetic fieldsof poles one and two. The third pole can include magnet segments 204 e,204 f, 204 g, 204 h. A fourth pole can include magnet segments 204 n,204 p, 204 q, 204 r. The magnetic field direction vectors of the thirdand fourth poles are also parallel and opposite to one another.

The examples illustrated in FIGS. 2H-2R and discussed above are notintended to limit the possible magnetic configurations contemplated forthe rotor hub 202. Indeed, several additional implementations and magnetconfigurations can also be implemented to meet a wide array of magneticand structural characteristics for particular rotor applications. Thefacet-based rotor concepts described above can be used to develop aversatile variety of potential rotor configurations. Indeed, where acommon rotor hub geometry is employed by a rotor manufacturer, commonmagnet segment geometries can be employed across rotor designs, allowingthe designer to build nearly limitless rotor variations by interchangingmagnet segments having the appropriate magnetic field vectors.Additionally, where rotor hubs 202 are employed allowing for magnetsegments with equal arcuate span, fabrication of the magnet segments andthe required magnet segment combinations can be simplified, in that onlymagnet segments of a single geometry need to be fabricated.Additionally, in designs employing magnet segments with the fewestdifferent magnetic profiles, the number of different magnet segmentsthat need to be manufactured and stocked can be further minimized,allowing rotor designers to provide a range of rotor products whileminimizing supply chain and manufacturing costs, among other advantages.

Referring now to FIG. 3A, an example electric machine 319 is shown. Theelectric machine 319 is similar to and may be used as the electricmachine 102 a shown in FIG. 1B. The electric machine 319 includes ahousing 314 defining an interior 308. A rotor 306 is rotatable relativeto the stator 300 and disposed in the interior 308 thereof. There is agap 310 between the stator 300 and rotor 306. The example stator 300includes an electromagnetic winding 302 mounted on a cylindrical statorcore 304. The stator 300 is suitable for use as stator 108 above. Someimplementations of the winding 302 can be configured for the electricmachine to function as a synchronous, AC electric machine. Someimplementations of the winding 302 can include two-pole windings,forming a three phase electromagnet. Other implementations are possibleas well, depending on the electric machine application, includingfour-pole windings, single-phase windings, and other windingconfigurations.

The winding 302 can be constructed by winding cable or formed conductorsthrough stator core slots to form the winding loops or coils. The statorcore 304 can be constructed of metallic, laminated plates, bondedtogether to form the core structure. The materials used in stator core304 plates can be selected so as to adjust the electromagnetic fluxcharacteristics of the winding 302 wound around the core slots. The corematerial can be selected also by considering the material used in thecable of the winding, so as to achieve a desired electromagnetic statorprofile. For example, copper-based, insulated cables can be used for thewinding 302. The cable can be wound around a core 304 built of steelplates laminated together with a silicon-based, low-loss laminate. It iscontemplated that the slots of the stator core 304, as described in moredetail below, can be implemented using a variety of slot shapes andsizes. The selection of the slot geometry can be based on the cable type(or types) used in the windings. Additionally, the winding 302 can beconstructed as form-wound or random-wound coils. In certain instances,the windings 302 result in winding end turns 312 positioned on the axialends of the stator core 304. As set forth in more detail below, variousend turn winding techniques can be used to provide for end turns 312with the particular structural and electromagnetic characteristicsdesired for a certain particular stator design.

Some implementations of the stator 300 can be adapted for subsea and/orcorrosive environment operation. For example, certain instances of thestator 300 can be sealed or otherwise protected from exposure to heattransfer fluids, process fluids, other corrosive or harmful matterand/or other foreign matter by providing a protective barrier 316 aroundthe stator 300 or otherwise sealing the stator 300. For example, certaininstances of the electric machine system may provide for a “flooded”system. A protective barrier 316 can be provided to guard againstcorrosion of elements of the stator 300 while allowing the fluidprovided in the electric machine system to cool the stator 300. Otherimplementations may provide a coating, or other seal on the stator, soas to seal the stator 300 from exposure or corrosion. For example, someor all of the stator can be coated or treated for corrosive resistancewith epoxy, polyetheretherketones, ethylene chlorotrifluoroethylenecopolymer and/or other treatments. Some implementations of stator 300can be provided with protective coverings that provide rigid structuralsupport as well as protection.

The stator, such as the stator shown in FIG. 3A, may be formed from astator core and windings 302 extending through the stator core. Anexample stator core 335 is shown in FIG. 3B. The stator core 335 isformed from a plurality of adjacent yokes 303 (i.e., a stator stack)extending in a longitudinal direction 305 bounded at opposing ends byend plates 307. Further, a plurality of stator bars 309 extend in thelongitudinal direction 305 and are operable to axially, radially andcircumferentially align the yokes 303. A plurality of teeth 301 areretained within slots or channels formed by the yokes 303, which isdiscussed in more detail below. See, e.g., FIG. 3G.

FIG. 3C illustrates a stator stack 325 formed from a pair of adjacentyokes 303. The stator stack 325, shown without stator teeth andelectromagnetic windings, is discussed in more detail below. Accordingto some implementations, a stator 300 may include a stack of eight yokes303. Other implementations, though, may include additional or feweryokes 303. One or more of the yokes 303 may be segmented. That is, oneor more of the yokes 303 may be formed from a plurality of arc-shapedsegments 315. In some implementations, all of the yokes 303 aresegmented.

As shown, the yoke 303 is formed from four segments 315 and, thus, theyoke 303 is divided into quadrants. However, in other instances, theyoke 303 may be formed from more or fewer segments 315. An examplesegment 315 is shown in FIG. 3D in which the segment 315 is formed froma plurality of laminations 311. The illustrated example segment 315 isformed from ten laminations 311, although other implementations may beformed from additional or fewer laminations 311. In someimplementations, the laminations 311 may be formed from steel, such aslow-loss silicon steel. In other implementations, the laminations 311may be formed from different types of steel or other types of metals,alloys, composites, or other types of suitable materials. Laminations311 may be bonded together chemically or mechanically. For example, thelaminations 311 may be bonded together with an adhesive. Alternately,the laminations 311 may be mechanically coupled by interlocking thelaminations 311 with each other. In some instances, a portion of onelamination 311 may protrude into an adjacent lamination 311. Further, insome implementations, some laminations 311 may interlock with adjacentlaminations 311 while other laminations 311 do not interlock with otherlaminations 311.

Each segment 315 includes a plurality of radially inward extendingprotrusions 317. The protrusions 317 define a plurality of first notches320 formed along an interior periphery 318 of the segment 315. As shownin the illustrated example, each segment 315 includes six protrusions317, although, in other instances, each segment 315 may include more orfewer protrusions 317 defining more or fewer first notches 320. As shownin FIG. 3C, the first notches 320 align to form at least a portion oftooth channels 321 that accept a tooth 301 (described in more detailbelow). Each segment 315 also includes a plurality of second notches 322formed on an outer perimeter 324 of the segment 315. As illustrated inFIG. 3C, the second notches 322 align to form at least a portion of achannel 326 into which a stator bar 309 is retained, as illustrated inFIG. 3B. The stator bar 309 retained in the channel 326 providesalignment and structural support to the assembled stator 300.

An example stator bar 309 is illustrated in FIG. 3E. The illustratedstator bar 309 is a slender member having a constant rectangularcross-section. As also illustrated in FIG. 3C, the channels 326 alsohave a constant rectangular cross-section to accept and retain thestator bars 309. However, the stator bar 309 shown in FIG. 3E and thechannel 326 shown in FIG. 3C are merely examples, and the stator bars309 and channels 326 may have other cross-sectional shapes.

Referring again to FIG. 3C, the yoke 303 is assembled such that joints313 formed at adjacent ends of the segments 315 are offset from eachother so that joints 313 in adjacent yokes 303 do not align. In otherimplementations, though, adjacent joints 313 may align. As shown, theangular offset (θ) of joints 313 in adjacent yokes 303 is 45°, althoughother angular offsets may be used. In certain instances, the yokes 303may be welded together, bonded together with an adhesive, assembled withfasteners, interlockingly coupled, and/or assembled in another manner.Still further, the assembled stator 300 and/or the stator core 335 maybe coated with polyetheretherketone (“PEEK”), ethylenechlorotrifluoroethylene copolymer (“ECTFE”), oxide coating and/oranother material.

FIG. 3F shows an example end plate 307 of the stator 300. The end plates307 are disposed at opposing ends of the of the assembled stator core335. In certain instances, the end plate 307 may be single, continuousplate. The end plate 307 also includes a plurality protrusions 331formed in an interior periphery 332 of the end plate 307. Theprotrusions 331 form first notches 330 therebetween. The end plate 307also includes a plurality of second notches 334 formed in an outerperiphery 336 of the end plate 307. When combined with the stator stackand teeth 301, protrusions 331 overlay the teeth 301 that are retainedin the tooth channels 321. The first notches 330 align with channelsformed between the teeth 301, i.e., winding channels 350, describedbelow. The second notches 334 align with the second notches 322 to formthe channels 326. In certain instances, as shown in FIG. 3G, the toothchannels 321 may have the shape of a dovetail-type joint such that theteeth 301 and associated tooth channels 321 interlock so that the teeth301 are locking retained therein. However, the channels 321 may form anyshape that retains the teeth 301. Further, the tooth channels 321 mayhave a high aspect ratio in certain instances, while, in otherinstances, the tooth channels 321 may have lower aspect ratios, i.e.,the tooth channels 321 may be shallower and wider.

Each tooth 301 may be formed from a plurality of tooth segments 338, anexample of which is shown in FIG. 3H. According to the illustratedexample, the tooth segment 338 has a tapered cross-section. A first end340 of the tooth segment 338 has a dimension D1 that is larger than adimension D2 of a second end 342 of the tooth segment 338. An end of theassembled tooth 301 corresponding to the first ends 340 of the toothsegments 338 are retained in the tooth channels 321.

In some implementations, the tooth segments 338 may be formed from aplurality of laminations 339. As shown, the example tooth segment 338 isformed from ten laminations. In other instances, the tooth segments 338may be formed from additional or fewer laminations. The teeth 301 may beformed from tooth segments 338 having the same or approximately the samelength. In other implementations, the teeth 301 may be formed from toothsegments 338 having different lengths. In some instances, the toothsegments 338 may have different lengths by having more or fewerlaminations 339 than other tooth segments 338. Laminations 339 may bechemically or mechanically bonded. For example, some of the laminations339 may be bonded together with an adhesive. In other instances, some ofthe laminations 339 may be interlockingly coupled. For example, aprotrusion formed in one lamination 339 may be received into areceptacle formed in an adjacent lamination 339.

In some implementations, one or more of the teeth 301 may be formed fromtooth segments 338 having different lengths. For example, FIG. 3K showsa schematic view of a tooth 301 extending through the channel 321. Thetooth 301 is formed from tooth segments 338 a and 338 b having differentlengths. In the implementation shown, the tooth segment 338 a has alength half of the length of tooth segment 338 b. Further, the length ofthe yokes 303 may be the same as the length of tooth segment 338 b. Asshown, the tooth 301 leads with a tooth segment 338 a abutting the endplate 307. The tooth segment 338 a occupies half the length of theportion of the channel 321 extending through the first yoke 303. A toothsegment 338 b is placed adjacent the tooth segment 338 a, causing thetooth segment 338 b to overlap the adjacent yoke 303. That is, a firsthalf of the tooth segment 338 b lies in one yoke 303 while the secondhalf of the tooth segment 338 b extends into the neighboring yoke 303.Overlapping of the tooth segments 338 b in the adjacent yokes 303provides rigidity and enhances mechanical strength of the stator 300.Although the tooth segments 338 b are described as overlapping by theadjacent yokes 303 by half, the tooth segments 338 b could overlap theadjacent yokes 303 by different amounts. For example, in someimplementations, the tooth segments 338 may overlap adjacent yokes 303in the following percentages: 60%-40%, 65%-35%, 70%-30%, or 80%-20%.However, it is within the disclosure to use any desired amount ofoverlap. Still further, the tooth segments 338 b may be of a length toextend partly into a first yoke 303, extend completely through one ormore adjacent yokes 303, and partially extend into an additional yoke303.

Referring to FIG. 3I, each tooth segment 338 may include a protrusion344 on first face 346 and a receptacle 348 on a second face 347. Theprotrusion 344 on one tooth segment 338 is accepted into the receptacle348 on an adjacent tooth segment 338 to provide for at least one ofalignment or attachment of adjacent tooth laminations. FIG. 3J showsanother configuration of the protrusions 344 and receptacles 348 formedon tooth segments 338.

According to some implementations, the teeth 301 may be formed from amaterial different from one or more of the yokes 303. Particularly, theteeth 301 may include a material that has a higher magnetic fluxcapacity than the material forming the yokes 303. In certain instances,the tooth segments 338 are formed, at least in part, from a cobalt-ironalloy. For example, one or more of the laminations 339 forming the toothsegment 338 may be formed from cobalt-iron alloy, while otherlaminations 339 may be formed from a different material. Examplecobalt-iron alloys include Hiperco, a product of Carpenter TechnologyCorporation, Silectron, a product of Arnold Magnetic TechnologiesCorporation, and/or other alloys. Still further, the tooth segments 338need not all be formed from the same material. That is, in someimplementations, some of the tooth segments 338 may be formed from onematerial and other tooth segments 338 formed of different materials. Incertain instances, since high magnetic flux material is typically moreexpensive than other materials, some portion of the tooth segments 338(e.g., one or more segments 338 or one or more laminations 339 of one ormore segments 338) may be formed of a high magnetic saturation fluxcapacity material and the remainder formed of a less expensive material.In certain instances, the less expensive material may be used to formone or more of the laminations 311. The different materials of toothsegments 338 or laminations 339 therein may be alternated in a regularor irregular pattern over the length of the stator 300. For example,every second, third, fourth or other specified tooth segments 338 may beformed from the higher magnetic saturation flux density material whilethe interstitial tooth segments 338 may be formed from less expensive,lower saturation flux density material. The resulting tooth 301 has ahigher composite magnetic saturation flux capacity than the lessexpensive material alone, but cost less than a tooth 301 made entirelyof the higher magnetic flux capacity material. In some implementations,the high magnetic saturation flux material may be distributed throughthe stator 300 so that the ends of the stator 300 have a relatively lowmagnetic saturation flux density. In other instances, the ends of thestator 300 may have the lowest magnetic saturation flux density.

In another example, the types of materials of the tooth segments 338(including the materials of the laminations 339 of the tooth segments338) at different locations along the tooth 301 can be selected toachieve a desired temperature distribution across the length of thestator 300 and/or to compensate for variations in heat extraction and/orgeneration along the length of the stator 300. In certain instances, thematerials of the tooth segments 338 can be configured to achieve auniform temperature distribution or a more uniform temperaturedistribution across the length of the stator 300 than achieved withtooth segments 338 of uniform material type. For example, a higherdensity (number per unit length) of higher magnetic flux material toothsegments 338 can be provided in areas of the stator 300 with lesscooling heat transfer. By increasing the magnetic flux capacity in theseareas, less heat is generated and the lesser cooling can be at leastpartially offset. Similarly, in areas with greater cooling heattransfer, a lower density of higher magnetic flux material toothsegments 338 can be provided. In certain instances, for example, wherethe heat transfer fluid is introduced through the ends of the rotor andstator 300, the tooth segments 338 or portions thereof near the axialcenter of a tooth 301 can have a higher density of higher magnetic fluxdensity material than tooth segments 338 near the ends of the tooth 301to offset the lower heat transfer at the axial center of the stator 300.

Referring again to FIG. 3G, the laminated teeth 301 are inserted intorespective tooth channels 321, as explained above. The assembled stator300 includes channels 350 that are formed between adjacent teeth 301.Cable and/or formed conductors may be fed through or placed into thesewinding channels 350 to form windings of the stator 300.

As described, the assembled stator 300 (shown in FIG. 3B) provides astator core that can achieve a higher flux density than if the teeth andyoke portions were made from the same material. Further, such aconstruction results in a cost savings by using more expensive materialsin only certain places, such as in the tooth region, where enhancedmagnetic flux density is needed and not in less critical areas, such asthe yoke. Further, construction of the yoke 303 from the plurality ofsegments 315 provides for less waste in manufacturing. Particularly,when producing the laminations 311, 339 to form the segments 315 ortooth segments 338, respectively, from sheet material, the laminations311 and 339 may be arranged more densely on the sheet, leaving lesswaste. Additionally, the tooth segments 338 and yoke segments 315 can bemass produced to further reduce manufacturing costs.

A stator of an electric machine, such as the stator 300 described above,may be assembled in an number of different manners. In certaininstances, the stator core 335 may be assembled by joining the four yokesegments 315 to form a yoke 303 and joining the appropriate number ofteeth segments 338 to the yoke 303) and then joining the resultingassemblies to one another, along with the end plates 307, to form thestator core 335. In certain instances, the stator core 335 may beassembled by forming complete teeth 301 (i.e., by joining the teethsegments 338 together to form complete teeth 301) and a complete statorstack (i.e., by joining together the plurality of yokes 303) and thenassembling the completed teeth 301 to the completed stator stack andadding the end plates 307 to form the stator core 335. In certaininstances, the stator core 335 may be assembled in another fashion. Thewindings 302 may be wound to the stator core 335 in a number ofdifferent manners. In certain instances, the windings 302 may be woundto the completed teeth 301 (e.g., the teeth 301 held in positionrelative to one another with a fixture) prior to assembly into thestator stack. In certain instances, the windings 302 may be wound to thecompleted stator core 335, i.e., after the stator stack and teeth 301are assembled together. The assembly of the windings 302 and teeth 301and/or the entire assembled stator 300 may be vacuum-pressureimpregnated with a coating material and baked, for example, to achievedesired mechanical and electrical properties. In certain instances,locking plates may be attached to the ends of the stator stack to securethe teeth 301 to the stator stack.

As mentioned above, construction of the stator 300 permits the use ofdifferent materials between the teeth and the yoke. Such a constructionallows optimization of flux density and reduction in losses and relatedconstruction costs. This assembly process has the further benefits ofusing winding techniques not otherwise achievable. Further, windingsformed in this way may have attached thereto cooling devices. Such acombination would not otherwise be possible with traditional windingtechniques.

FIGS. 3L-3Q illustrate implementations of the protective barrier 316formed around a stator, such as the stator 300 or 108 of an electricmachine, such as the electric machine 102. The protective barrier 316forms a stator cavity 353 in which the stator 300 resides. The statorcavity 353 may or may not be filled with a fluid. FIG. 3L shows across-sectional view of an example electric machine, which may besimilar to the electric machine 102. The electric machine includes ahousing 314, the stator 300, the rotor 306, and the protective barrier316. The protective barrier 316 may also prevent intrusion of fluidpassing through the electric machine 102 into the stator cavity 353. Theprotective barrier 316 has a cylindrical shape, a closed end 354 at aninner radius, and an open end 356 at an outer radius. The closed end 354is formed by a cylinder 358, and the open end 356 is defined by sideflanges 360. The side flanges 360 abut and/or are attached to thehousing 314. As explained above, the protective barrier 316 providesprotection for the stator 300, for example, in flooded applications inwhich the electric machine 102 has fluid (represented by arrows 362)passing therethrough between the rotor 306 and the stator 300.Accordingly, the protective barrier 316 provides protection againstexposure of the electric machine and its components to the fluid (e.g.,sea water, cooling fluids, process fluids) or other foreign matterpassing through the electric machine.

Additionally, the protective barrier 316 protects the electric machineby preventing contact between the stator 300 and the rotor 306. Further,the protective barrier 316 may be formed of a material resistant tocorrosion and/or abrasion, such as abrasion and/or corrosion that may becaused by the fluid (including any particulates and/or contaminantscontained therein) passing through the electric machine 102 between thestator 300 and the rotor 306. The protective barrier 316 may also beconstructed to withstand pressure changes between the fluid passingthrough the electric machine and any fluid contained in the statorcavity 353. The protective barrier 316 may also be constructed toaccommodate thermal expansion and contraction of the housing 314 and thestator 300.

FIG. 3M shows a partial cross-sectional view of an example electricmachine. As shown, the cylinder 358 of the protective barrier 316includes a first portion 364 and an abutting second portion or ring 366.In certain instances, the cylinder 358 can be a common commerciallyavailable pre-formed tubing. According to some implementations, a firstedge 368 of the first portion 364 of the cylinder 358 may include anoutwardly flared portion 370 and a tapered portion 372. The taperedportion 372 extends from the outwardly flared portion 370. The taperedportion 372 is accepted into a tapered channel 374 formed in one of theside flanges 360. The tapered portion 372 and the tapered channel 374may be fit together to provide a seal. For example, the tapered portion372 and the tapered channel 374 may be fit together with an interferencefit. In certain instances, the seal prevents the passage of fluid.Further, the tapered channel 374 includes at least one opening 376extending from an inner portion of the tapered channel to the atmosphereor to the stator cavity 353, for example. The at least one opening 376allows air to escape from the channel during assembly of the taperedportion 372 into the tapered channel 374, thereby providing a securedattachment.

A first edge 378 of the ring 366 may also be tapered and, similarly, maybe accepted into another tapered channel 374 formed in a second of theside flanges 360. The first edge 378 of the ring 366 and the taperedchannel 374 may also be fitted together with an interference fit toprovide a seal against intrusion of fluid. Also, as described above, thetapered channel 374 may include one or more openings 376, describedabove, to provide escape of air from the tapered channel 374 (i.e.,pressure equalization) during assembly of the first edge 378 and thetapered channel 374.

Second edges 382 and 384 of the first portion 364 and ring 366,respectively, overlap to form a tapered joint 386. Particularly, in someimplementations, adjacent surfaces of the second edges 382, 384 of thefirst portion 364 and the ring 366, respectively, overlap and abutagainst each other to form the tapered joint 386. The tapered jointforms a seal to prevent passage of fluid. In certain instances, thesecond edge 382 of the first portion 364 may flare outwardly. Thetapered joint 386 allows dimensional variations of the protectivebarrier 354 while still maintaining a seal to prevent intrusion of fluidinto the stator cavity 353. For example, during operation of theelectric machine 102, components of the electric machine 102 mayexperience expansion and/or contraction, such as due to rotationalspeeds and/or temperature changes and the tapered joint 386 may remainengaged. In certain instances, the tapered joint 386 may form awater-tight seal. Further, a contact pressure between the first portion364 and the ring 366 at the tapered joint 386 may increase withexpansion of the housing 314. Alternately, the tapered joint 386 may beconfigured such that the pressure of the tapered joint 386 may increasewith contraction of the housing 314.

According to some implementations, either or both of the first portions364 or ring 366 of the cylinder 358 (i.e., the portion proximate thepermanent magnets of the rotor), may be formed from a fiber and polymercomposite material. In certain instances, the cylinder 358 may be formedfrom a carbon or glass fiber composite material provided in athermoplastic or thermosetting matrix. Such materials provide highstrength, corrosion resistance, and abrasion resistance and are notmagnetically permeable. In certain instances, the side flanges 360 maybe formed from a metal.

FIG. 3N shows another implementation of the protective barrier 354without a tapered joint. In such an implementation, the cylinder 358includes opposing tapered edges 388 are accepted into flared channels374. The tapered edges 388 and the tapered channels 374 may also form aninterference fit to create a seal. In certain instances, the seal may bea water-tight seal to prevent intrusion of fluid. Also, as explainedabove, the tapered channels 374 may include one or more openings 376 toprovide pressure equalization during assembly. Further, the cylinder 358may be formed from a composite material, as described above, and thefibers of the composite may be oriented and/or the matrix materialselected such that the coefficient of thermal expansion of the cylinder358 matches the coefficient of thermal expansion of the housing 314,thereby eliminating the need for a tapered joint. In certain instances,the cylinder 358 can be a common commercially available pre-formedtubing.

The implementation shown in FIG. 3O shows a protective barrier 354formed from a composite material having a coefficient of thermalexpansion that matches that of the housing 314. In this implementation,the cylinder 358 has an integrated side flange 392 and a tapered edge388. As explained above, the tapered edge 388 may be fitted into thetapered channel 374 to provide an interference fit. Pressure may beequalized in the tapered channel 374 and the atmosphere via one or moreopenings 376 formed in the side flange 360 from the tapered channel 374and the stator cavity 353. The integrated side flange 392 may be secureddirectly to the housing 314 by a ring 394 that may also function toprotect an outer edge 396 of the integrated side flange 392. In certaininstances, the ring 394 may be formed from metal.

FIGS. 3P and 3Q show additional alternate implementations of theprotective barrier 354. The protective barriers 354 illustrated in theseimplementations may also be formed from a composite material designed tohave a coefficient of thermal expansion that matches that of the housing314. As shown in FIG. 3P, the cylinder 358 of the protective barrier 354may include a lip 398 that includes an outer surface 391 that abuts aninner surface 393 of the side flange 360. A ring 395 may be used toclamp the cylinder 358 in place such that the lip 398 is sandwichedbetween the ring 395 and the side flange 360. In some implementations,the ring 395 and the side flange 360 may be formed from metal, and, instill other implementations, the ring 395 and side flange 360 may beformed from the same type of metal. One or more fasteners may be used tosecure the ring 395, cylinder 358, and side flange 360 together.Alternately or in combination, an adhesive may be used.

FIG. 3Q shows another implementation in which an inner surface 381 ofthe cylinder 358 at outer edges 397 abut an outer surface 383 of theside flanges 360. A ring 385 may be used to secure the cylinder 358 tothe side flanges 360 at the outer edge 397. In some implementations,fasteners and/or an adhesive may be used to secure the ring 385,cylinder 358, and side flanges 360 together. In addition to thesemethods or alternatively, the ring may have a slightly larger outerdiameter than an inner diameter of the cylinder 358. Thus, the ring 395and cylinder 358 may be held in place relative to the side flange 360 byfriction caused by an interference fit. Also, the ring 385 and the sideflanges 360 may be formed from a metal, and, in still other instances,the ring 385 and the side flanges 360 may be formed from the same typeof metal.

FIG. 4A is a partial schematic end view of an example core 400 of astator for an electric machine. The example core 400 is suitable for usein the stator 108 of electric machine 102. The core 400 defines asubstantially cylindrical inner volume to receive a rotor of an electricmachine. The core 400 includes teeth 402 extending radially from a yoke422 of the core to an outer circumference of the inner volume of thecore. The teeth define slots 404 to receive conductive windings. Forexample, neighboring teeth 402 a and 402 b define slot 404 a, andneighboring teeth 402 b and 402 c define slot 404 b. Each tooth 404 hasa tip 420. As shown, for example in FIGS. 4A, 4B, and 4C, a stator canhave slots between each pair of teeth, where each slot has a slot regionwith parallel slot sides and each tooth has a tooth section withparallel tooth sides.

Each tooth 402 has a radial length extending from the yoke 422 to thetip 420 of the tooth. For example, tooth 402 a has a radial lengthextending from the yoke 422 to tip 420 a, and tooth 402 b has a radiallength extending from the yoke 422 to tip 420 b. In the illustratedexample, all of the teeth 402 have the same radial length. In someimplementations, some of the teeth 402 have unequal radial lengths. Eachslot 404 has a radial depth extending from the yoke 422 to the innervolume. The radial depth of a slot 404 can be defined by the yoke 422and the sides of the teeth 402 that define the slot 404. For example,the radial depth of the slot 404 a is defined by the yoke 422 and thesides of the teeth 402 a and 402 b, and the radial depth of the slot 404b is defined by the yoke 422 and the sides of the teeth 402 b and 402 c.

Each tooth 402 has a width along the radial length of the tooth 402. Forexample, the width of a tooth at a given point is related to theazimuthal angle spanned by the tooth at the given point. A tooth 402 mayhave a first radial section where the tooth width is constant orsubstantially constant along the radial length of the tooth 402. Assuch, a tooth can have parallel tooth sides in at least a section of thetooth. A tooth 402 may have a second radial section where the toothwidth varies along the radial length of the tooth 402. As such, a toothcan also have non-parallel sides in at least a section of the tooth. Thetooth width may vary linearly and/or non-linearly along the radiallength of the tooth in the second radial section. The radial length andthe width of a tooth can determine an area of the tooth. For example,the area of a tooth may be calculated as an integral of the tooth widthover the radial length of the tooth.

Each slot 404 has a width along the radial depth of the slot 404. Forexample, the width of a slot at a given point is related to theazimuthal angle at the given point between the two teeth 402 that definethe slot 404. A slot 404 may have a first radial section where the slotwidth is uniform or substantially uniform along the radial depth of theslot 404. As such, a slot can have parallel slot sides in at least aregion of the slot. A slot 404 may have a second radial section wherethe slot width varies along the radial depth of the slot 404. As such, aslot can also have non-parallel sides in at least a region of the slot.The slot width may vary linearly and/or non-linearly along the radialdepth of the slot in the second radial section. The radial depth and thewidth of a slot can determine an area of the slot. For example, the areaof a slot may be calculated as an integral of the slot width over theradial depth of the slot.

The geometry (e.g., length, depth, width, area) of the teeth 402 and theslots 404 can influence performance and efficiency aspects of the stator(and hence, of the electric machine). The geometry of a slot 404 caninfluence the position, distribution, and/or cross-sectional area of theconductive coils that can be installed in the slot. A ratio of slot areato tooth area of the core 400 may influence a maximum power, a powerfactor, and/or an efficiency achievable with the core 400. Teeth with afirst radial section where the tooth width varies along the radiallength of the tooth and a second radial section where the tooth width isuniform along the radial length of the tooth may define slots with afirst radial section where the slot width varies or is uniform along theradial depth and a second radial section where the slot width varies.Slots with a first radial section where the slot width varies along theradial depth and a second radial section where the slot width is uniformalong the radial depth can improve the performance and/or efficiency ofthe electric machine. A core having this type of slot may balance autilization of a stator core material (e.g., iron or another material)and a conductive winding material (e.g., copper, or another material).For example, slots with a first radial section where the slot widthvaries along the radial depth and a second radial section where the slotwidth is uniform along the radial depth can allow a largercross-sectional area of conductive material in a portion of the slot,and can prevent excess iron in various portions of the tooth (e.g., the“root” of the tooth near the yoke 422). Slots having this configurationmay accommodate both cable windings (e.g., in the first section) andformed windings (e.g., in the second section). In some cases, excesscore material at a tooth root includes magnetically under-utilizedmaterial. In some cases, increasing flux density at the tooth tip 420limits the flux loading of the electric machine and allows excessiveflux leakage path across the slot 404, which may degrade machineperformance.

In the example core 400 of FIG. 4A, all of the teeth 402 and slots 404are identical. The radial section 406 b of the tooth 402 b has a widththat varies along the radial length of the tooth 402 b, and the radialsection 410 b of the tooth 402 b has a uniform width along the radiallength of the tooth 402 b. The radial section 408 b of the slot 404 bhas a uniform width along the radial depth of the slot 404 b, and theradial section 412 b of the slot 404 b has a width that varies along theradial length of the slot 404 b. The cross-section of each slot 404 hastwo rounded corners at the yoke 422. The rounded corners can accommodatecoils having a round cross-section, such as the cable winding coilsshown in FIG. 4B. Each tooth 402 in FIG. 4A has a broad tip 420 that mayenhance the flux and/or other properties of the core 400.

FIG. 4B is a partial schematic end view of the example core 400 of FIG.4A. FIG. 4B illustrates example conducting coils installed in the slot404 b. The illustrated coils are the coils of cable windings. Coils 414a, 414 b, 414 c, and 414 d reside in the section 408 b of the slot 404b. Coils 414 e, 414 f, 414 g, 414 h, 414 i, 414 j, 414 k, and 414 lreside in the section 412 b of the slot 404 b.

FIG. 4C is a partial schematic end view of an example core of a statorfor an electric machine. The example core 400 can be the core of thestator 108 of electric machine 102. In the example core 400 of FIG. 4C,all of the teeth 402 and slots 404 are identical. The radial section 406b of the tooth 402 b has a width that varies along the radial length ofthe tooth 402 b, and the radial section 410 b of the tooth 402 b has auniform width along the radial length of the tooth 402 b. The radialsection 408 b of the slot 404 b has a uniform width along the radialdepth of the slot 404 b, and the radial section 412 b of the slot 404 bhas a width that varies along the radial length of the slot 404 b. Thecross-section of each slot 404 has two substantially square corners atthe yoke 422. The substantially square corners can accommodate coilshaving a cross section with square corners, such as the formed windingcoils 416 shown in FIG. 4C.

FIG. 4C illustrates example conducting coils installed in the slot 404b. Some of the illustrated coils are the coils of formed windings, andsome of the illustrated coils are the coils of cable windings. Formedwinding coils 416 a and 416 b reside in the section 408 b of the slot404 b. Cable winding coils 414 reside in the section 412 b of the slot404 b. Each tooth 402 in FIG. 4C has a narrowed tip 420 that may enhancethe flux and/or other properties of the core 400.

FIG. 4D is a partial schematic end view of an example core 400. FIG. 4Dillustrates example angular parameters where each tooth includes twosections having non-parallel sides. A first section of each tooth hasnon-parallel sides at a first angle, and second section of each toothhas non-parallel sides at a second angle. The first angle and the secondangle are different. In the example shown, the first angle is 1.9degrees, and the second angle is 0.7 degrees larger than the first angel(i.e., 2.6 degrees). Other angles and/or angle differences may be used.

FIG. 4E is a partial schematic end view of an example core of a statorfor an electric machine. The example core 400 can be the core of thestator 108 of electric machine 102. In the example core 400 of FIG. 4E,all of the teeth 402 and slots 404 are identical. The radial section 406b of the tooth 402 b has a uniform width along the radial length of thetooth 402 b, and the radial section 410 b of the tooth 402 b has a widththat varies along the radial length of the tooth 402 b. The radialsection 408 b of the slot 404 b has a width that varies along the radialdepth of the slot 404 b, and the radial section 412 b of the slot 404 bhas a uniform width along the radial length of the slot 404 b. Thecross-section of each slot 404 has two substantially rounded corners atthe yoke 422. The substantially rounded corners can accommodate coilshaving a round cross section, such as the rounded coils of cablewindings.

In FIG. 4E, some of the illustrated coils are the coils of formedwindings, and some of the illustrated coils are the coils of cablewindings. Cable winding coils 414 reside in the section 408 b of theslot 404 b. Formed winding coils 416 c and 416 d reside in the section412 b of the slot 404 b. Each tooth 402 in FIG. 4E has a narrowed tip420 that may enhance the flux and/or other properties of the core 400.

FIG. 4F is a schematic end view of example end turns of a stator 450 foran electric machine. The example stator 450 can be used for the stator108 of electric machine 102. Only the end turns 452 of the stator 450and a portion of the core 454 of the stator 450 are illustrated in FIG.4F. The stator 450 includes other parts that are not illustrated in FIG.4F.

The stator 450 includes formed windings. The coils of the formedwindings include axial sections (not illustrated in FIG. 4F) that extendthe axial length of the stator core. The coils of the formed windingsinclude multiple end turns 452 that form an end turn bundle beyond theaxial end of the stator core. The end turn bundle includes two groups ofend turns 452 that form four interleaved radial layers 464 of end turns452. Each group forms two of the four layers 464. One layer in eachgroup is radially between the two layers of the other group.

The stator 450 includes a core 454 that defines an inner bore 451, whichis a substantially cylindrical inner volume to receive a rotor of anelectric machine. As shown in FIG. 4G, the core 454 has multiple teeth456 extending radially inward, toward the bore 451; the teeth 456 defineslots 458 to receive conductive windings (e.g., formed windings, cablewindings, or another type). The coils of the windings include axialsections (not shown in FIG. 4G) that span an axial length of the core.Each axial section may extend between the two axial ends of the core.The coils of the windings include end turns 452 extending beyond theaxial end of the core. Each end turn 452 connects two axial sections ofa coil. The axial sections of one or more coils may reside in each slot.Each end turn 452 has a first end connecting to a first axial sectionand a second end connecting to a second axial section. As shown in FIG.4G, the first end of each end turn connects at a first circumferentiallocation, and the second end of each end turn connects at a secondcircumferential location. In the implementation shown in FIG. 4G, thefirst end connects at a first radial distance from the radial center ofthe core, and the second end connects at a second radial distance fromthe radial center of the core. In some implementations, both ends of anend turn connect to axial sections of a coil at the same radial distancefrom the center of the core.

An end turn bundle, as illustrated in FIG. 4F, can include multiplegroups of end turns 452. Each group of end turns 452 can form layers 464at different radii around the radial center of the core 454. A singleend turn 452 primarily resides in two layers formed by one of thegroups. For example, an end turn 452 a has a first portion in a layer464 a, and the end turn 452 a has a second portion in a different layer464 c. As another example, an end turn 452 b has a first portion in alayer 464 b, and the end turn 452 b has a second portion in a differentlayer 464 d. The layers 464 a and 464 c are formed by a first group ofend turns 452 radially positioned as the end turn 452 a. Each end turn452 in the first group is offset circumferentially from the othermembers of the first group. The layers 464 b and 464 d are formed by asecond group of end turns 452 radially positioned as end turn 452 b.Each end turn 452 in the second group is offset circumferentially fromthe other members of the second group. Layer 464 a is radially inside oflayer 464 b; layer 464 b is radially inside of layer 464 c; layer 464 cis radially inside of layer 464 d. Thus, the first group of end turns(radially configured as end turn 452 a) and the second group of endturns (radially configured as end turn 452 b) are interleaved to formfour layers of end turns.

Each end turn 452 passes through a planar cross-section parallel to theend of the core 454. Each end turn 452 of the first group of end turnsforms two layers of end turns, passing through the planar cross-sectionat a first radius and a third radius. The first radius is less than thethird radius. Each end turn 452 of the second group of end turns formstwo different layers, passing through the planar cross-section at asecond radius and a fourth radius. The second radius is less than thefourth radius. The first group of end turns and the second group of endturns are interleaved, such that the second layer is between the firstlayer and the third layer (i.e., the first radius is less than thesecond radius, and the second radius is less than the third radius) andthe third layer is between the second layer and the fourth layer (i.e.,the second radius is less than the third radius, and the third radius isless than the fourth radius).

Each end turn 452 extends between the two ends of the end turn to form apartial loop extending from the core 454. In some implementations, whentwo groups of end turns are interleaved, each end turn in one grouppasses through the partial loop formed by one or more of the end turnsin the other group. For example, the end turn 452 a passes through thepartial loop formed by the end turn 452 b.

In some cases, an end turn bundle including two groups of end turns thatform four interleaved radial layers of end turns can form an end turnbundle that is longitudinally shorter than other configurations. Forexample, if the two groups of end turns were not interleaved, andinstead the two groups formed fewer than four layers of end turns, theend turn bundle may be almost twice as long as the four-layer bundle. Alonger end turn bundle consumes more axial space in the electricmachine, and may cause the rotor bearing journals to be positionedfarther apart. A shorter end turn bundle consumes less axial space inthe electric machine, and may allow the rotor bearing journals to bepositioned closer together. When the rotor bearing journals are axiallycloser together, the bearing journals may suffer less stress and damageand/or provide better stability for the rotor. Thus, an end turn bundlethat includes two interleaved groups of end turns may consume less axialspace in the electric machine, may allow less axial distance betweenrotor bearing journals, and/or may reduce wear and/or damage to parts ofthe electric machine. In some cases, an end turn bundle that includestwo interleaved groups of end turns may consume approximately half ofthe axial space that the end turn bundle would consume in otherconfigurations.

FIG. 4H is a partial schematic side view of the example stator 450. FIG.4I is a partial schematic side view of a portion of the core 454 andexample end turns 452 a, 452 b of a stator 450. FIG. 4J is a schematiccross-sectional view from near the axial center of the example stator450 toward the axial end of the example stator 450. FIG. 4K is a partialschematic view of end turns 452 a and 452 b of a stator 450.

FIG. 4L is a schematic of an example end turn 460 and an example endturn 4200. The example end turn 460 can be included in the stator 108 ofelectric machine 102. The example end turn 460 can be included in a lapwinding configuration that includes two interleaved sets of end turnsthat form an end turn bundle having four radial layers. The example endturn 4200 is designed for a traditional lap winding configuration thatdoes not include interleaved sets of end turns. In their respectiveconfigurations in stators of substantially equal radial dimension, theexample end turns 460 and 4200 can span the same azimuthal angle. FIG.4L includes example dimensions of the end turns 460 and 4200. In somecases, an end turn has different dimensions.

FIG. 4M is a schematic perspective view of example end turns 460 and aportion of a stator core 462. The radial dimension of the stator ismapped to a linear dimension in FIG. 4M for purposes of illustration.The end turns 460 represent the end turns 452 in a rectilinearcoordinate system. The core 462 represents the core 454 in a rectilinearcoordinate system. The end turns 460 include two groups of end turnsthat form four interleaved radial layers of end turns represented in arectilinear coordinate system. A first group of end turns, that includesend turn 460 a, includes multiple end turns at the same radial positionas end turn 460 a and circumferentially offset from end turn 460 a. Asecond group of end turns, that includes end turn 460 b, includesmultiple end turns at the same radial position as end turn 460 b andcircumferentially offset from end turn 460 b.

FIG. 4N is a schematic perspective view of the portion of the examplestator core 462 and the example end turns 460 a and 460 b represented ina rectilinear coordinate system. As illustrated in FIG. 4N, the ends ofthe end turns 460 and the core 462 define gaps 466 in the slots of thestator core. Each slot includes two gaps. One gap is between the ends oftwo different end turns. A gap 466 a is formed in a first slot at afirst radius between the stator core and the end of an end turn residingin the first slot; a gap 466 b is formed in a second slot at a secondradius between the ends of two end turns residing in the second slot; agap 466 c is formed in the first slot at a third radius between the endsof two end turns residing in the first slot; and a gap 466 d is formedin the second slot at a fourth radius beyond the end of an end turnresiding in the second slot. In some cases, coolant fluid (e.g., air,nitrogen, or another gas) can flow through the gaps 466 in the slots tocool the conductive windings. For example, the gaps 466 can extendaxially between the axial ends of the stator and provide a coolant flowpath along all or part of the axial length of the stator. Coolant fluidcan flow between the axial sections of the conductive windings in thestator core (e.g., in gaps 466 b and 466 c). Coolant fluid can flowbetween an axial section of the conductive windings and the stator core(e.g., in gap 466 a). Coolant fluid can flow between an axial section ofthe conductive windings and the rotor (e.g., in gap 466 d). The coolantcan flow from a mid-stack inlet to a volume surrounding the end turns tocool the end turns and the axial sections of the windings. The coolantcan flow to a mid-stack outlet from a volume surrounding the end turnsto cool the end turns and the axial sections of the windings. Coolantcan additionally or alternatively flow in an gap between the rotor andthe stator.

In some cases, the slots have alternating depths. For example, some ofthe slots in the core 462 may have a shallow slot depth, eliminating orreducing the volume of the gap 466 a. This may enhance magnetic fluxproperties of the stator.

FIG. 4O is a schematic perspective view of example end turns representedin a rectilinear coordinate system. Only two end turns 460 a and 460 bare shown in FIG. 4O for clarity of illustration.

An end turn bundle that includes two groups of end turns interleaved toform four layers of end turns can include formed windings, cablewindings, or a combination thereof. FIGS. 4F, 4G, 4H, 4I, 4J, 4K, 4L,4M, 4N, and 4O illustrate aspects of an example of a formed end turnbundle that includes two groups of formed end turns interleaved to formfour layers of formed end turns. Each of the illustrated end turns ofFIGS. 4F, 4G, 4H, 4I, 4J, 4K, 4L, 4M, 4N, and 4O can be built usingstandard end turn-forming equipment. However, some un-illustratedimplementations may require non-standard end-turn-forming processes.FIGS. 4P, and 4Q illustrate an example of a cable end turn bundle thatincludes two groups of cable end turns interleaved to form four layersof cable end turns.

FIG. 4P is a schematic side view of an example end turn bundle 470 of astator of an electric machine. The example end turn bundle 470 can beincluded in the stator 108 of electric machine 102. FIG. 4Q is aschematic perspective view of the example end turn bundle 470. FIG. 4EEis a schematic end view of the example end turn bundle 470. FIG. 4FF isa schematic end view of two end turns of the example end turn bundle470. FIG. 4GG is a schematic end view of four end turns of the exampleend turn bundle 470. FIG. 4HH is a schematic side view of two end turnsof the example end turn bundle 470. FIG. 4II is a schematiccross-sectional view of the end turn bundle 470, viewed from near theaxial center of an example stator toward the axial end of the examplestator.

The illustrated example end turn bundle 470 includes cable windings. Thecoils of the cable windings include axial sections (not illustrated inFIGS. 4P, 4Q, 4EE, 4FF, 4GG, 4HH, and 4II) that extend the axial lengthof a stator core. The coils of the cable windings include a plurality ofend turns that form the end turn bundle 470 beyond the axial end thestator core. The end turn bundle 470 includes two groups of end turnsthat form four interleaved radial layers of end turns. The first groupof end turns includes end turns 4001 a, 4001 c, and 4001 e. The secondgroup of end turns includes end turns 4001 b and 4001 d. Each groupforms two of the four layers. The first group forms a first (outermost)layer of end turns and a third layer of end turns. The second groupforms a fourth (innermost) layer of end turns and a second layer of endturns. One layer in each group is radially between the two layers of theother group. In particular, the second layer is radially between thefirst and third layers, and the third layer is radially between thesecond and fourth layers.

As shown in FIGS. 4FF, 4GG, and 4II, the two groups of end turns in theexample end turn bundle 470 form only two radial layers at an axialsection of the end turn bundle closest to the stator. In particular, allof the end turns in the end turn bundle 470 exit the end face of thecore at a first radius on the end face and reenter the core at a secondradius on the end face. The first group of end turns (including 4001 a,4001 c, and 4001 e) exit the core through the end face of the core at anexit location on the first radius, turn toward the first radial layer,extend through the first radial layer, turn toward the third radiallayer, extend through the third radial layer, and reenter the corethrough the end face at a reentry location on the second radius. In theexample shown, before reentering the core, the first group end turnseach curve radially inward from the third layer toward the secondradius.

The second group of end turns (including 4001 b and 4001 d) exit thecore through the end face at an exit location on the first radius, turntoward the second radial layer, extend through the second radial layer,turn toward the fourth radial layer, extend through the fourth radiallayer, and reenter the core through the end face at a reentry locationon the second radius. In the example shown, each end turn in the secondgroup accommodates a neighboring coil in the first group. For example,as shown in FIG. 4GG, the end turn 4001 d exits the end face on thefirst radius, turns radially outward, extends through the second layerof end turns, turn radially inward, extends through the fourth layer ofend turns, turn radially inward to accommodate the end turn 4001 e, andthen turns radially outward to reenter the end face on the secondradius.

FIGS. 4R and 4S show partial schematic end views of example cores 400 ofa stator for an electric machine. The example cores 400 can be the coreof the stator 108 of electric machine 102. The example cores 400 includeslots 404 having different shapes according to some implementations ofthe electric machine. Although the slots 404 are shown as including aneven number of coils 414, an odd number of coils 414 may be used. Insome implementations, the shape of the slots 404 may carry a windingthat includes coils in a lap winding configuration and coil in aconcentric winding configuration, although the slots shapes may be usedin other types of windings.

As shown in FIG. 4R, each slot 404 includes a first slot region 421holding coils 414 and a second slot region 419 holding coils 414. Thefirst slot region 421 is defined by two non-parallel opposing slot sideportions 415 c and 415 d. The second slot region 419 is defined by twoparallel opposing slot side portions 415 a and 415 b. The slot sideportions 415 a and 415 c form part of one side of the slot. The slotside portions 415 b and 415 d form part of another side of the slot. Theslot side portions 415 a and 415 c define a first angle at 417 a, andthe slot side portions 415 b and 415 d define a second angle at 417 b.The first angle and the second angle are different angles, as shown inFIG. 4R. For example, the first angle at 417 a is an obtuse angle lessthan 180 degrees, and the second angle at 417 b is 180 degrees. Otherangles may also be used.

FIG. 4T shows a partial schematic end view of an example core 400 of astator for an electric machine in which the slots 404 include an oddnumber of coils 414. In the example shown, the coils 414 include coils414A, 414B, and 414C. Although the coils 414A and 414B are shown asincluding an even number of coils, the coils 414A and 414B may includean odd number of coils. Further, the coils 414A may be a left-hand coilside of lap coils, and the coils 414B may be a right-hand coil side oflap windings. The coils 414C are the coils of concentric windings. Thus,by including the coils 414C in each slot 404, the number of total coils414 contained in each slot 404 is made an odd number. By having an oddnumber of coils in each slot, the voltage of the associated electricmachine may be changed at smaller incremental levels, providing bettercontrol of the electric machine output.

FIG. 4U shows another core 400 in which the coils 414 may be differentsizes to provide better nesting or packing of the coils 414 within theslots 404. The coils 414A and the coils 414B may be of one size wire orcable, while the coils 414C may be at a different size, such as asmaller size. The different size coils provide for a more closely packedslot 404. Additionally, any of the coils 414A, 414B, or 414C may beproduced by a single turn winding process but multiple cables may bewound in parallel. Further, a generally triangular or trapezoidalcross-section wedge 1000 may be included in one or more of the slots 404to maintain the coils 414A and/or 414B in a packed state. Over time andoperation of the electric machine, the coils may relax in the slots,which may have an adverse effect on machine performance. For example, ifthe coils become loose inside the slot, the coils may sag and/or shiftin the slot. As a result, the coils may be subject to damage due tovibration and/or chafing. Accordingly, the wedges 1000 are included inthe slot to maintain the coils 414A and/or 414B in a packed condition.According to some implementations, the wedges 1000 may apply a biasingforce on the coils to maintain the coils in a packed state. For example,the wedge 1000 may have a longitudinal curvature, as shown in FIG. 4V.In some implementations, the wedge 1000 becomes stressed when the wedge1000 is inserted in a slot, and the stress results in the biasing forceexerted on the coils in the slot. The biasing force applied by the wedge1000 may hold the coils in a substantially fixed position, which mayeliminate or reduce slack and/or sagging in the coils. For example, thewedge 1000 in the slot may hold the coils in place and prevent damagethat could be caused by loose, sagging, and/or shifted coils.

In FIG. 4V, the example wedge 1000 is illustrated as having aC-cross-section. The wedge 1000 may be positioned in the slots 404 asshown in FIGS. 4U and 4Z with the open portion of the C-cross-sectionfacing the radial center of the core 400. Alternately, the wedge 1000may be inserted into the slots 404 so that the open portion of C-crosssection faces away from the radial center of the core 400. The wedgesmay have other shapes. Planar strips 1002 may also be used.

In some implementations, for example when the wedge 1000 is positionedas shown in FIGS. 4U and 4Z with the open end of the wedge 1000 facingthe center of the core 400, the cooling properties of the machine may beenhanced. Friction between the rotor and fluid surrounding the rotor(e.g., fluid in the machine gap between the rotor and the stator) cangenerate heat. To prevent overheating, cooling fluid (e.g. air oranother type of fluid) may be directed through the machine gap betweenthe rotor and the stator. The wedge 1000 can be configured toeffectively increase the volume of the machine gap, as illustrated inFIGS. 4U and 4Z. For example, the wedge 1000 open to the center of thecore 400 and the planar strip 1002 effectively lead to an increase inthe volume of the machine gap. The increased volume in the machine gapmay reduce demands on the machine's cooling system. For example, theincreased volume may reduce the pressure drop along the machine gap,which may thus reduce the demands placed on the blower or pump thatgenerates the flow of cooling fluid through the machine gap.

FIGS. 4AA-4DD show other example configurations of coils 414 and wedges1000 in a stator 400 of an electric machine. FIG. 4AA shows a stator 400that includes a first plurality of coils 414A in a lap windingconfiguration and a second plurality of coils 414B in concentric windingconfiguration. (The coils 414A in a lap winding configuration areunshaded in FIGS. 4AA-4DD, and the coils 414B in a concentric windingconfiguration are shaded in FIGS. 4AA-4DD.) The slots 404 of FIG. 4AAeach have the same shape and carry the same number of conductors. InFIG. 4AA, each slot carries a concentric coil 414B having one turn, andeach slot carries a wedge 1000. The concentric coils 414B shown in FIG.4AA can be wired in a “1-1-1” concentric coil configuration of a twopole, three phase electric machine. The “1-1-1” concentric coilconfiguration is discussed further with respect to FIG. 4W.

FIG. 4BB shows a stator 400 that includes a first plurality of coils414A in a lap winding configuration and a second plurality of coils 414Bin a concentric winding configuration. The stator 400 of FIG. 4BBincludes slots having different shapes. For example, the slots 404C and404D have the same shape and each carry ten conductors, but the slot404E has a different shape than the slots 404C and 404D and carries nineconductors. In FIG. 4BB, slots 404C and 404D each carry a concentriccoil 414B having two turns, while slot 404E carries a concentric coil414B having one turn. Also in FIG. 4BB, each of the slots includes awedge 1000. The concentric coils 414B shown in FIG. 4AA can be wired ina “2-2-1” concentric coil configuration of a two pole, three phaseelectric machine.

FIG. 4CC shows a stator 400 that includes a first plurality of coils414A in a lap winding configuration and a second plurality of coils 414Bin a concentric winding configuration. The stator 400 of FIG. 4CCincludes slots having different shapes. For example, the slots 404C and404E have the same shape and each carry nine conductors, but the slot404D has a different shape than the slots 404C and 404E and carries tenconductors. In FIG. 4CC, slots 404C and 404E each carry a concentriccoil 414B having one turn, while slot 404D carries a concentric coil414B having two turns. Also in FIG. 4CC, each of the slots includes awedge 1000. The concentric coils 414B shown in FIG. 4CC can be wired ina “2-1-2/1-2-1” concentric coil configuration of a two pole, three phaseelectric machine.

FIG. 4DD shows a stator 400 that includes a first plurality of coils414A in a lap winding configuration and a second plurality of coils 414Bin a concentric winding configuration. The stator 400 of FIG. 4DDincludes slots that all have the same shape, but do not all carry thesame number of conductors. For example, the slots 404C and 404D eachcarry ten conductors, but the slot 404E carries nine conductors. In FIG.4DD, slots 404C and 404D each carry a concentric coil 414B having twoturns, while slot 404E carries a concentric coil 414B having one turn.Also in FIG. 4DD, each of the slots includes either a first wedge 1000Aor a second wedge 1000B. The first wedge 1000A in the slots 414C and414D is smaller to leave more space for the conductors in the slots 414Cand 414D. The second wedge 1000B in the slot 414E is larger and leavesless space for the conductors in the slot 414E. The concentric coils414B shown in FIG. 4DD can be wired in a “2-2-1” concentric coilconfiguration of a two pole, three phase electric machine.

FIG. 4JJ is a schematic cross-sectional view of an example core 400 foran electric machine. The core 400 defines multiple slots, and each slotcarries conductive coils 414 and a wedge. Two different types of wedgesare shown in FIG. 4JJ. A first type of wedge 1004 has a C-shapedcross-sectional profile. FIG. 4MM shows a perspective view of theexample wedge 1004. A second type of wedge 1006 has an E-shapedcross-sectional profile. FIG. 4LL shows a perspective view of theexample wedge 1006. Both of the wedges 1004 and 1006 define holes 1008that allow fluid to flow radially from a first region of the slot to asecond region of the slot. For example, in the slots that carry aC-shaped wedge 1004, the wedge 1004 defines a first region 1005 in theslot, and the coils 414 reside in a second region in the slot. The firstregion 1005 allows an axial flow of cooling fluid through the slot. Theholes 1008 defined in the wedge 1004 allow fluid to flow from the firstregion 1005 to the second region in order to cool the coils 414. Theholes 1008 also allow fluid to flow from the second region into thefirst region 1005, for example, after the fluid has contacted the coils414. As another example, in the slots that carry an E-shaped wedge 1006,the wedge 1006 defines a first region 1009 in the slot, and the coils414 reside in a second region in the slot. The first region 1009 allowsaxial flow of cooling fluid through the slot. The holes 1007 defined inthe wedge 1006 allow fluid to flow from the first region 1009 to thesecond region in order to cool the coils 414. The holes 1007 also allowfluid to flow from the second region into the first region 1005, forexample, after the fluid has contacted the coils 414.

Each wedge may define multiple holes along the axial length of thewedge, as shown in FIGS. 4LL and 4MM. The holes may be spaced at regularintervals, random intervals, or in another manner. A single wedge 1006or 1004 may define holes of different sizes, shapes, or dimensions inorder to control fluid flow to the coils 414. For example, larger holesmay be defined in some locations on a wedge 1006 in order to promote agreater flow rate through the larger holes, and smaller holes may bedefined in other locations on the wedge 1006 in order to limit a flowrate through the smaller holes. The size, shape, spacing, and otherparameters of the holes in a wedge may be configured to improve coolingin a stator of an electrical machine and thereby improve efficiency ofthe electrical machine. Thus, in some cases, a wedge can be used as aflow control device within the stator. In FIGS. 4LL and 4MM, a singlehole is defined at each of multiple locations along the axial length ofthe wedge. In some implementations, there may be multiple holes definedat each location along the axial length.

The wedges 1004 and 1006 may have a longitudinal curvature, as the wedge1000 shown in FIG. 4V. As a result of the longitudinal curvature, thewedges 1004 and 1006 may exert a biasing force on the coils 414 thathelps stabilize the coils 414 within a slot. For example, the biasingforce exerted by a wedge may prevent sagging of the coils 414.

As seen in FIG. 4PP the wedges can be formed in two or more parts, suchas a first part 1028 and a second part 1032, longitudinally separated bya shim or stack of shims 1030. When installed in the slot, the firstpart 1028 would reside adjacent the open end of the slot and the secondpart 1032 would reside adjacent the coils. Different thicknesses of theshim or shim stack 1030 can be selected to control the force exerted bythe second part 1032 on the coils. For example, the first and secondparts 1028, 1032 can be installed into a given slot, and one or moreshims 1032, of the same and/or different thickness, added to increasethe force exerted by the second part 1032 on the coils. In certaininstances, different slots of the same electric machine may requiredifferent shims to achieve the same force exerted on the coils. The shimor shim stack 1030 can be installed after one or more of the first part1028 or second part 1032 is installed in the slot to facilitateachieving the desired force without damaging the insulation or coatingof the coils. Alternately, the shim or shim stack 1030 can be installedsubstantially simultaneously with installing the first and second parts1028, 1032. The shims 1032 thus allow for an adjustable tight fitbetween the wedge, the coils and the slot without damaging the cablesduring wedge insertion. Although shown as solid, the first and/or secondparts 1028, 1032 can each have a C-shaped cross-section or othercross-section providing an axial channel for fluid flow and holes forradial flow, as described above.

FIG. 4KK is a schematic cross-sectional view of an example core 400 foran electric machine. The core 400 in FIG. 4KK defines multiple slots,and each slot carries coils 414 and a wedge 1010. The C-shaped wedges1010 each define holes 1012 that allow fluid to flow radially betweenregions of the slot.

FIG. 4NN is an is a schematic end view of an example core 400 havingwedges 1014 similar to any of the configurations described above, and/orof another configuration, retained using retaining rings 1016. The wedgeretaining rings 1016 encircle the central opening in the stator core 400and are fixed (e.g., by bolt, screw and/or otherwise) to the end face ofthe core 400. Retaining rings 1016 can be provided at both ends of thestator core 400 to capture the wedges 1014 and prevent the wedges 1014from moving axially along the stator core 400. The retaining rings 1016have slots that receive and interlock with protrusions 1020 at the endsof each wedge 1014, preventing the wedges 1014 from moving radially. Theretaining ring 1016 also press the wedges 1014 against the top of thestator slot. In instances, such as FIG. 4PP, where the wedges are formedin multiple parts and/or include one or more shims, the retaining ring1016 can also retain the multiple wedge parts and shims. FIG. 4OO is aperspective view of an example C-shaped wedge 1014 better illustratingthe protrusion 1020 and also having holes 1026. The C-shaped defines anaxial passage 1024 through the wedge 1014. As seen in FIG. 4NN, theretaining rings 1016 can have apertures 1022 that align with the axialpassage 1024 to allow flow of fluids through the retaining rings 1016.

FIG. 4QQ shows an slot liner 1034 for lining the interior of a statorslot in a stator core 400 of an electric machine. The slot liner 1034 ismade of a flexible, tear and temperature resistant film, such aspolyester, polyamide and/or other material. FIG. 4QQ shows the liner1034 laid flat. When installed in a slot, as in FIG. 4RR, the liner 1034extends from the slot at both ends of stator core 400, and can be foldedonto the end faces of the stator core 400. The protruding ends of liner1034 are clamped to the end faces of the stator core 400 with aretaining ring (as in FIG. NN) and/or with other clamps to retain theliner 1034 in position. FIG. 4RR shows single bar clamps 1036 a,retained to the end face with fasteners 1038 (e.g., bold, screw and/orother fastener), that clamp a portion of two adjacent liners to the endof the stator core 400. FIG. 4SS shows U-shaped clamps 1036 b, likewiseretained to the end face with fasteners 1038. The clamps can be retainedto the stator core 400 in other manners. The slot liners 1038 areinstalled prior to winding the coils into the slots to protect cablesand the insulation on the cables during winding. In certain instances,the liners 1034 can be removed from the slots. In certain instances, theliners 1034 can remain in the slots while the remainder of the electricmachine is assembled, and remain in the slots during operation of theelectric machine. Because the slot liners 1034 are retained against theend faces of the stator core 400 the liners resist shifting duringwinding and subsequent operation of the machine, and prevent the cablesfrom rubbing against the stator core. In instances where the liners 1034will be removed, a multipart wedge and shim(s) (as in FIG. 4PP) can beused such that with the shim not installed, the coils are loose in theslot and the liner 1034 can more easily withdrawn from the slot.Thereafter, the shim would be installed to secure the coils in theslots.

FIG. 4W shows a windings schematic according to some implementations.The windings scheme shown in FIG. 4W utilizes both concentric coils andlap coils in a single stator. The schematic illustrates windings of atwo pole, three phase electric machine. The letter group A, A′, a, anda′ represent the first phase winding. The letter group B, B′, b, and b′represent the second phase winding. The letter group C, C′, c, and c′represent the third phase winding. The three coils represented by A andA′ are the lapped portion of the first phase winding. The three coils aand a′ represent the concentric portion of the first phase winding. Thesolid and dashed lines represent the end turn connections for the firstphase winding. Each line may represent a single or multiple turns. Theend turn connections for the second and third phase are not shown, butthe same connection configuration for the first phase may also be usedfor the second and third phases.

FIG. 4W shows an example of a “1-1-1” concentric coil configuration. Inthe “1-1-1” concentric coil configuration shown, each of the three coilsof the concentric portion of the first phase winding includes a singleturn. As such, each slot of the stator in the “1-1-1” concentric coilconfiguration carries the same number of turns, namely one turn each.The concentric coils 414B shown in FIG. 4AA are in a “1-1-1” concentriccoil configuration. More generally, an “n-n-n” concentric coilconfiguration carries “n” concentric coil turns in each slot. Examplevalues of “n” can include 1, 2, 3, . . . 10, and higher values. Othertypes of concentric coil configurations are also possible. Other exampleconcentric coil configurations include a “2n-n-2n/n-2n-n” concentriccoil configuration (e.g., the “2-1-2/1-2-1” concentric coilconfiguration shown in FIG. 4CC, or another), a “2n-2n-n” concentriccoil configuration (e.g., the “2-2-1” concentric coil configurationshown in FIG. 4DD, or another), and/or others. Example values of “n” caninclude 1, 2, 3, . . . 10, and higher values.

Two other example concentric coil configurations are shown in FIGS. 4Xand 4Y. FIG. 4X shows an example of a “2-1-1” concentric coilconfiguration. In the “2-1-1” concentric coil configuration shown, theoutermost coil of the concentric portion of the first phase windingincludes a two turns, and each of the two inner coils of the concentricportion of the first phase winding include a single turn. As such,different slots of the stator in the “2-1-1” concentric coilconfiguration carry different numbers of turns. In particular, a firstslot carries two turns of the concentric portion of the first phasewinding, and a second and a third slot each carry only one turn of theconcentric portion of the first phase winding. Other types of “2n-n-n”concentric coil configurations may also be used. Example values of “n”can include 1, 2, 3, 10, and higher values.

FIG. 4Y shows an example of a “2-1-0” concentric coil configuration. Inthe “2-1-0” concentric coil configuration shown, the concentric coilconfiguration includes two concentric coils for each phase winding andthree lap coils for each phase winding. The outer concentric coilincludes a two turns, and the inner concentric coil includes one turn.As such, different slots of the stator in the “2-1-0” concentric coilconfiguration carry different numbers of turns. In particular, a firstslot carries two turns of the concentric portion of the first phasewinding, a second slot carries one turn of the concentric portion of thefirst phase winding, and a third slot carries no concentric coil turns.Other types of “2n-n-0” concentric coil configurations may also be used.Example values of “n” can include 1, 2, 3, . . . 10, and higher values.

FIGS. 4TT, 4UU, 4VV, 4WW, and 4XX show a solid model of an examplestator 4100 of an electric machine that includes the windingsrepresented in the diagram of FIG. 4W. The example stator 4100 can beused for the stator 108 of electric machine 102. FIGS. 4TT and 4VV areperspective views of a first end of the example stator 4100. FIG. 4UU isan end view of the example stator 4100, viewed from the first end of thestator. FIG. 4WW is a side view of a second end of the example stator4100. FIG. 4XX is a perspective view of the second end of the examplestator 4100. As shown in FIGS. 4TT, 4UU, 4VV, 4WW, and 4XX, the examplestator includes an elongate stator core 4102 and three conductivewindings carried by the core 4102. A first winding includesconcentric-wound coils 4104 a and lap-wound coils 4106 a. A secondwinding includes concentric-wound coils 4104 b and lap-wound coils 4106b. A third winding includes concentric-wound coils 4104 c and lap-woundcoils 4106 c. The letter labels A, A′, B, B′, C, and C′ for thelap-wound coils and the letter labels a, a′, b, b′, c, and c′ for theconcentric-wound coils are included to show correspondence with FIG. 4W.While the end turns of the coils are primarily visible in FIGS. 4TT,4UU, 4VV, 4WW, and 4XX, the coils also include axial portions thatextend between the end turns within the stator core 4102. As shown inFIG. 4UU, the elongate core 4102 is adapted to internally receive arotor of an electric machine.

The coils in each winding are connected in series. Each coil may includemultiple turns connected in series or in parallel. Each slot can carryan odd number of turns or an even number of turns. In someimplementations, the slots in the stator 4102 do not all carry the samenumber of turns. In some implementations, the concentric-wound coils ina winding all have a first number of turns, and the lap-wound coils inthe same winding all have a second number of turns, unequal to the firstnumber of turns. Installing one or more of the coils may include forminga winding structure outside of the core 4102 and installing the formedwinding structure in the core 4102. Installing one or more of the coilsmay include successively forming each of the individual coils in thecore 4102.

The core 1402 includes a first end face 4108 a shown in FIGS. 4TT and4VV. The core 1402 includes a second, opposing end face 4108 b shown inFIGS. 4WW and 4XX. The coils 4104 a, 4104 b, 4104 c, 4106 a, 4106 b, and4108 c each define a loop that extends axially through the elongate core4102, exits the core 4102 through the end face 4108 a at an exitlocation, and reenters the core through the end face 4108 a at a reentrylocation. Each of the coils spans a distance on the end face between itsexit location and its reentry location.

The lap-wound coils 4106 a in the first winding each span a distancethat is substantially equal to the distance spanned by each of the otherlap-wound coils 4106 a in the first winding, while the concentric-woundcoils 4104 a in the first winding each span a distance that is unequalto a distance spanned by any of the other concentric-wound coils 4104 ain the first winding. Similarly, the lap-wound coils 4106 b in thesecond winding each span a distance that is substantially equal to thedistance spanned by each of the other lap-wound coils 4104 b in thesecond winding, the concentric-wound coils 4104 b in the second windingeach span a distance that is unequal to the distance spanned by any ofthe other concentric-wound coils 4104 b in the second winding, thelap-wound coils 4106 c in the third winding each span a distance that issubstantially equal to the distance spanned by each of the otherlap-wound coils 4106 c in the third winding, and the concentric-woundcoils 4104 c in the third winding each span a distance that is unequalto the distance spanned by any of the other concentric-wound coils 4104c in the third winding.

The distance on the end face spanned each coil can be an angulardistance on the end face between the exit location of the coil and thereentry location of the coil. For example, when the end face of the coredefines a circumference, the distance on the end face spanned by a coilcan be an angle between the exit location of the coil and the reentrylocation of the coil with respect to the center point of thecircumference. In the example, each coil defines a mid-point on thecircumference between its exit location and its reentry location. Forthe concentric-wound coils 4104 a, 4104 b, and 4104 c, the mid-point ofeach coil is substantially at the same angle on the circumference as themid-point of each other concentric-wound coil in the same winding. Forthe lap-wound coils 4106 a, 4106 b, and 4106 c, the mid-point of eachcoil is at a different angle on the circumference than the mid-point ofany other lap-wound coil in the same winding.

The core 4102 includes teeth that extend radially toward an axial centerof the core 4102. The teeth define radial slots between the teeth, andthe coils are carried in the slots. Thus, the core defines an array ofslots to carry the windings. Each coil resides in a pair of non-adjacentslots, and thus, each coil spans a number of slots between thenon-adjacent slots in which the coil resides. Each of the lap-woundcoils 4106 a in the first winding spans a number of slots that is equalto the number of slots spanned by each of the other lap-wound coils 4106a in the first winding, while each of the concentric-wound coils 4104 ain the first winding spans a number of slots that is unequal to thenumber of slots spanned by any of the other concentric-wound coils 4104a in the first winding. For example, each of the lap-wound coils 4106 aspans eight slots, while the three concentric-wound coils 4104 a span 6,8, and 10 slots, respectively. Similarly, each of the lap-wound coils4106 b in the second winding spans a number of slots that is equal tothe number of slots spanned by each of the other lap-wound coils 4106 bin the second winding, each of the concentric-wound coils 4104 b in thesecond winding spans a number of slots that is unequal to the number ofslots spanned by any of the other concentric-wound coils 4104 b in thesecond winding, each of the lap-wound coils 4106 c in the third windingspans a number of slots that is equal to the number of slots spanned byeach of the other lap-wound coils 4106 c in the third winding, and eachof the concentric-wound coils 4104 c in the third winding spans a numberof slots that is unequal to the number of slots spanned by any of theother concentric-wound coils 4104 c in the third winding.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made. Accordingly, otherimplementations are within the scope of the following claims.

1. A rotor for an electric machine comprising: a rotor hub; a pluralityof permanent magnets disposed about the rotor hub; a first sleevecircumjacent the plurality of permanent magnets; and a second sleevecomprising a metal tape substantially helically wrapped over the firstsleeve.
 2. The rotor of claim 1, wherein the wrapped metal tape formsbutt laps over an outer surface of the first sleeve.
 3. The rotor ofclaim 1, wherein the first sleeve is a non-metallic sleeve.
 4. The rotorof claim 1, wherein the first sleeve is formed from a fiber and resincomposite material.
 5. The rotor of claim 1 further comprising first andsecond end rings disposed adjacent to opposing ends of the rotor hub,wherein a first end of the metal tape is bonded to the first end ringand a second end of the metal tape is bonded to the second end ring. 6.The rotor of claim 1, wherein the metal tape is applied under tension.7. The rotor of claim 1, wherein the second sleeve is cylindrical. 8.The rotor of claim 1, wherein the metal tape is treated with anonconductive surface treatment.
 9. The rotor of claim 1, wherein thesecond sleeve axially extends beyond opposing edges of the first sleeve.10. The rotor of claim 1, wherein the metal tape is non-magnetic.
 11. Anelectric machine comprising: a rotor comprising: a rotor hub; aplurality of permanent magnets disposed about the rotor hub; a firstsleeve circumjacent the plurality of permanent magnets; and a secondsleeve comprising a metal tape wrapped over the first sleeve.
 12. Theelectric machine of claim 11, wherein the wrapped metal tape forms buttlaps over an outer surface of the first sleeve.
 13. The electric machineof claim 11, wherein the first sleeve is a non-metallic sleeve.
 14. Theelectric machine of claim 11, wherein the first sleeve comprises a fiberand resin composite material.
 15. The electric machine of claim 11further comprising first and second end rings disposed adjacent toopposing ends of the rotor hub, wherein a first end of the metal tape isbonded to the first end ring and a second end of the metal tape isbonded to the second end ring.
 16. The electric machine of claim 11,wherein the metal tape is applied under tension.
 17. The electricmachine of claim 11, wherein the second sleeve is cylindrical.
 18. Theelectric machine of claim 11, wherein the metal tape is coated with anonconductive surface treatment.
 19. The electric machine of claim 11,wherein the second sleeve axially extends beyond opposing edges of thefirst sleeve.
 20. The electric machine of claim 11, wherein the metaltape is non-magnetic.
 21. A rotor for an electric machine comprising: arotor hub that includes a plurality of permanent magnets; a compositesleeve about the rotor hub; and a helically-wrapped metal-tape sleeveabout the composite sleeve.
 22. The rotor of claim 21, wherein thecomposite sleeve comprises a fiber and resin composite material.
 23. Therotor of claim 21, wherein the metal tape is non-magnetic.
 24. The rotorof claim 21, wherein the helically-wrapped metal-tape sleeve extendsbeyond one or more axial ends of the composite sleeve.
 25. The rotor ofclaim 21, wherein the rotor further comprises a first end ring at afirst end of the rotor hub and a second end ring at a second end of therotor hub, and the helically-wrapped metal-tape sleeve is bonded to thefirst end ring and the second end ring.